2010 United States Senate elections

Shading indicates party with largest share of that line. Does not include the January 2010 special election in Massachusetts.

Parties									Total
		Democratic	Republican	Independent	Libertarian	Green	Constitution	Others
Last elections (2008) Before the November elections		57	41	2[lower-alpha 3]	—	—	—	—	100
Not Up	Total	38	23	2[lower-alpha 3]	—	—	—	—	63
	Class 1 (2006→2012)	19	10	2[lower-alpha 3]	—	—	—	—	31
	Class 2 (2008→2014)	19	13	—	—	—	—	—	32
Up	Total	19	18	—	—	—	—	—	37
	Class 1	2	—	—	—	—	—	—	2
	Class 2	1	—	—	—	—	—	—	1
	Class 3	16	18	—	—	—	—	—	34
Incumbent retired	Total before	6[lower-alpha 4]	6	—	—	—	—	—	12
	Held by same party	3	6	—	—	—	—	—	9
	Replaced by other party	3 Democrats replaced by 3 Republicans		—	—	—	—	—	3
	Result after	3	9	—	—	—	—	—	12
Incumbent ran	Total before	13[lower-alpha 5][lower-alpha 6]	12[lower-alpha 7]	—	—	—	—	—	25
	Won re-election	10[lower-alpha 5]	10	—	—	—	—	—	20
	Lost re-election	2 Democrats replaced by 2 Republicans		—	—	—	—	—	2
	Lost renomination but won re-election	—	1	—	—	—	—	—	1
	Lost renomination but party held	—	1	—	—	—	—	—	1
	Lost renomination and party lost	1 Democrat replaced by 1 Republican		—	—	—	—	—	1
	Result after	10[lower-alpha 5]	15	—	—	—	—	—	25
Total elected		13[lower-alpha 5]	24	—	—	—	—	—	37
Net gain/loss		6	6	—	—	—	—	—	6
Nationwide vote	Votes	32,405,787	34,616,463	155,846[lower-alpha 8]	776,327	552,006	178,860	3,100,833[lower-alpha 8]	71,786,122
	Share	45.14%	48.22%	0.22%	1.08%	0.77%	0.25%	4.32%	100%
Result		51	47	2[lower-alpha 3]	—	—	—	—	100
End of this Congress		56	42	2[lower-alpha 3]	—	—	—	—	100

Source: Clerk of the U.S. House of Representatives[1]

Several sites and individuals publish predictions of competitive seats. These predictions look at factors such as the strength of the incumbent (if the incumbent is running for reelection) and the other candidates, and the state's partisan lean (reflected in part by the state's Cook Partisan Voting Index rating). The predictions assign ratings to each seat, indicating the predicted advantage that a party has in winning that seat.

Most election predictors used:

• "tossup": no advantage
• "tilt" (used by some predictors): advantage that is not quite as strong as "lean"
• "lean": slight advantage
• "likely" or "favored": significant, but surmountable, advantage
• "safe" or "solid": near-certain chance of victory

Where a site gives a percentage probability as its primary indicator of expected outcome, the chart below classifies a race as follows:

• Tossup: 50-55%
• Tilt: 56-60%
• Lean: 61-75%
• Likely: 76-93%
• Safe: 94-100%

Seven November races, as well as the Massachusetts special election in January, had margins less than 10%:

California was the tipping point state, where Barbara Boxer (D) defeated Carly Fiorina (R) by a margin of 10.0%.

Alabama election

Nominee Richard Shelby William G. Barnes Party Republican Democratic Popular vote 967,861 515,049 Percentage 65.3% 34.7%

County results

U.S. senator before election Richard Shelby Republican Elected U.S. Senator Richard Shelby Republican

Incumbent Republican Richard Shelby won re-election to a fifth term. On November 9, 1994, Shelby switched his party affiliation from Democratic to Republican, one day after the Republicans won control of both houses in the midterm elections, giving the Republicans a 53-47 majority in the Senate. He won his first full term as a Republican in 1998 by a large margin, and faced no significant opposition in 2004 and 2010.

Shelby had over $17 million in the bank, one of the highest of any candidate in the country. He had become even more popular in his opposition to the Troubled Asset Relief Program (TARP) and the Emergency Economic Stabilization Act of 2008, as the ranking member of the Senate Banking Committee.

In May, Shelby told reporters "I don't even know who my opponent is."[8]

Alaska election

Candidate Lisa Murkowski Joe Miller Scott McAdams Party Republican Republican Democratic Popular vote 101,091 90,839 60,045 Percentage 39.5% 35.5% 23.5%

Borough and census area results

U.S. senator before election Lisa Murkowski Republican Elected U.S. Senator Lisa Murkowski Republican

The November general election in Alaska was preceded by primary elections which were held August 24, 2010. Scott McAdams, the Mayor of Sitka, became the Democratic nominee and Joe Miller, an attorney and former federal magistrate, became the Republican nominee after defeating incumbent Senator Lisa Murkowski[10] in the Republican primary.[11]

Murkowski garnered more than 100,000 write-in votes in the general election, many of which were challenged by Miller for various errors including minor misspellings. The appeal was denied[12] Even if all the challenged votes were thrown out, Murkowski would have still had a lead of over 2,100 votes.[13]

Arizona election

Nominee John McCain Rodney Glassman Party Republican Democratic Popular vote 1,005,615 592,011 Percentage 58.7% 34.5%

County results

U.S. senator before election John McCain Republican Elected U.S. Senator John McCain Republican

Incumbent Republican John McCain, who returned to the Senate after losing the presidency to Barack Obama in the 2008 presidential election, ran for re-election to a fifth term and won.[19]

After spending over $20 million during the primaries, McCain still had more than $1million cash on hand after the primary election. Glassman criticized McCain on women's issues.[21] In August 2010, Glassman released a TV advertisement called "Arizona First."[22]

Arkansas election

Nominee John Boozman Blanche Lincoln Party Republican Democratic Popular vote 451,617 288,156 Percentage 57.90% 36.95%

County Results

U.S. senator before election Blanche Lincoln Democratic Elected U.S. Senator John Boozman Republican

Incumbent Democrat Blanche Lincoln ran for re-election to a third term, but lost to Republican nominee John Boozman. Boozman became the first Republican in 138 years to win the seat. Arkansas had previously only elected one Republican senator since the Reconstruction, who was defeated after his first term in 2002 by Mark Pryor.

The Republican primary was held May 18, 2010, with early voting from May 3–17.

California election

Nominee Barbara Boxer Carly Fiorina Party Democratic Republican Popular vote 5,218,441 4,217,366 Percentage 52.2% 42.2%

County results

U.S. senator before election Barbara Boxer Democratic Elected U.S. Senator Barbara Boxer Democratic

Incumbent Democrat Barbara Boxer won re-election to a fourth term.

In 2009, Boxer was criticized for correcting a general who called her "ma'am". Brigadier General Michael Walsh was testifying on the Louisiana coastal restoration process in the wake of Hurricane Katrina and answered Boxer's query with "ma'am" when Boxer interrupted him. "Do me a favor," Boxer said. "can you say 'senator' instead of 'ma'am?'" "Yes, ma'am," Walsh interjected. "It's just a thing, I worked so hard to get that title, so I'd appreciate it. Thank you," she said. The Army's guide to protocol instructs service members to call members of the U.S. Senate "sir", "ma'am" or "senator".[28][29] Fiorina used this incident prominently in campaign ads, as did David Zucker, who directed a humorous commercial for RightChange.com titled 'Call Me Senator.' In February 2010, Carly Fiorina put out a campaign ad attacking Republican rival Tom Campbell featuring a "demon sheep", creating international, mostly negative, publicity.[30]

Colorado election

Nominee Michael Bennet Ken Buck Party Democratic Republican Popular vote 851,590 822,731 Percentage 48.1% 46.4%

County results

U.S. senator before election Michael Bennet Democratic Elected U.S. Senator Michael Bennet Democratic

In December 2008, President-elect Barack Obama selected incumbent U.S. Senator Ken Salazar to become U.S. Secretary of the Interior.[31] After Salazar resigned from his seat,[32] Democratic Governor Bill Ritter appointed Denver Public Schools Superintendent Michael Bennet to fill the seat, who won re-election to his first full term.[33][34]

This was one of the most expensive elections in the 2010 cycle, with more than $50 million spent total, including over $35 million in outside spending.[36] Conservative third party groups hammered Bennet for voting 92% of the time with the Democratic leadership, including voting for healthcare reform and the stimulus package.[37] Liberal third party groups called Buck extremist. Bennet focused on attacking Buck's views on abortion, which he believed should be banned including those of cases of rape and incest. He was also attacked for wanting to eliminate the 17th Amendment[38] and refusing to prosecute an alleged rapist as Weld County district attorney. Planned Parenthood mounted a mail campaign, targeting women voters with the warning that "Colorado women can't trust Ken Buck." Bennet won the women vote by 17 points according to exit polls. After the election, Buck conceded to the Denver Post that the main reason why he lost is because of social issues.[39]

Connecticut election

Turnout	45.9% (voting eligible)
Nominee Richard Blumenthal Linda McMahon Party Democratic Republican Popular vote 636,040 498,341 Percentage 55.2% 43.2%
County results
U.S. senator before election Chris Dodd Democratic Elected U.S. Senator Richard Blumenthal Democratic

Incumbent Democrat Christopher Dodd suffered from dropping approval ratings in the past few years due to major controversies, leading him to announce in January 2010 that he would retire, instead of seeking a sixth term.[42] As Dodd was a Democrat, Richard Blumenthal, incumbent State Attorney General, announced on the same day that he would run for Dodd's seat.[43] The Connecticut Democratic Party nominated Blumenthal on May 21. Businesswoman Linda McMahon won the state party's nominating convention and the August 10 Republican primary to become the Republican candidate.[44]

Note: Blumenthal also appeared on the line of the Connecticut Working Families Party and received 30,836 votes on it. His Working Families and Democratic votes have been aggregated together on this table.

Delaware special election

Nominee Chris Coons Christine O'Donnell Party Democratic Republican Popular vote 174,012 123,053 Percentage 56.6% 40.0%

County results

U.S. senator before election Ted Kaufman Democratic Elected U.S. Senator Chris Coons Democratic

This was a special election to fill Delaware's Class 2 Senate seat, then held by Ted Kaufman, an appointee. The seat had been previously held by long-time Senator Joe Biden, who vacated it when he became Vice President of the United States in 2009.

Florida election

Nominee Marco Rubio Charlie Crist Kendrick Meek Party Republican Independent Democratic Popular vote 2,645,743 1,607,549 1,092,936 Percentage 48.9% 29.7% 20.2%

County results

U.S. senator before election George LeMieux Republican Elected U.S. Senator Marco Rubio Republican

Incumbent Republican Senator Mel Martínez, who was elected in a very close race against Democrat Betty Castor with 49% of the vote in 2004, announced on December 2, 2008, that he would not run for re-election to a second term,[49] then announcing on August 7, 2009, that he would resign prior to the end of his term.[50] The Governor of Florida, Republican Charlie Crist, was required to appoint a successor and he chose his former Chief of Staff, George LeMieux. LeMieux, a placeholder who did not run in the election, replaced Martínez in the Senate on September 10, 2009.

Crist publicly announced he was running for the seat in mid-2009. When he declared his candidacy, he received many Republican endorsements, including the National Republican Senatorial Committee, Martínez, and 2008 Republican presidential nominee John McCain. However, his support of the American Recovery and Reinvestment Act of 2009 hurt his popularity among conservatives, and Tea Party candidate Marco Rubio, the former Speaker of the Florida House of Representatives, surged in the polls. In April 2010, Crist announced he would drop out of the Republican primary and run as an Independent. The National Republican Senatorial Committee withdrew its endorsement of Crist and demanded a refund of its campaign funds that it provided for the Crist campaign.[51][52][53] Rubio went on to win the Republican primary against only token opposition.

Polling initially showed Crist neck and neck with Rubio, but by the end of August Rubio opened up a solid and consistent lead. He was supported by Republican and some Independent voters whereas Democratic and other Independents were split between Crist and Meek. Rubio went on to win the election with 49% of the vote to Crist's 30% and Meek's 20%.

Georgia election

Nominee Johnny Isakson Mike Thurmond Party Republican Democratic Popular vote 1,489,904 996,516 Percentage 58.3% 39.0%

County Results

U.S. senator before election Johnny Isakson Republican Elected U.S. Senator Johnny Isakson Republican

Incumbent Republican Johnny Isakson won re-election to a second term.[58]

Hawaii election

Nominee Daniel Inouye Cam Cavasso Party Democratic Republican Popular vote 277,228 79,939 Percentage 74.8% 21.6%

County Results

U.S. senator before election Daniel Inouye Democratic Elected U.S. Senator Daniel Inouye Democratic

Incumbent Democrat and President pro tempore Daniel Inouye won re-election to his ninth term.

Hawaii last elected a Republican Senator in 1970, and its current delegation to the United States Congress currently consists entirely of Democrats. Democrats have also won Hawaii's electoral votes in every presidential election since Ronald Reagan's landslide election in 1984. The exceptions at the time were then-Governor Linda Lingle (who was serving her second and final term) and then-U.S. Representative Charles Djou, both of whom were Republicans.

Idaho election

Nominee Mike Crapo Tom Sullivan Party Republican Democratic Popular vote 319,953 112,057 Percentage 71.2% 24.9%

County results

U.S. senator before election Mike Crapo Republican Elected U.S. Senator Mike Crapo Republican

Incumbent Republican Mike Crapo won re-election to a third term.

Sullivan, a heavy underdog, criticized Crapo for being in Washington for too long saying "Senator Crapo has been in Congress for 18 years. The country is struggling, and I think it's time to make a change." Crapo emphasized his conservative record in Washington.[65]

Illinois election

Nominee Mark Kirk Alexi Giannoulias Party Republican Democratic Special election 1,677,729 47.3% 1,641,486 46.3% Regular election 1,778,698 48.0% 1,719,478 46.4%

U.S. senator before election Roland Burris Democratic Elected U.S. Senator Mark Kirk Republican

Incumbent Democrat Roland Burris did not run in 2010.[66] He suffered from poor approval ratings[67] and was investigated by the Sangamon County, Illinois State's Attorney for perjury.[68] Although no criminal charges were filed against him, he faced an investigation by the Senate Ethics Committee.[69]

There were two ballot items for the same seat: a regular election, to fill the Class 3 seat beginning with the 112th United States Congress beginning on January 3, 2011, and a special election, to fill that seat for the final weeks of the 111th Congress, replacing the temporary appointment of Roland Burris to the vacancy created by Barack Obama's election to the presidency.[70]

A federal court ruled that the candidates appearing on the ballot for the replacement election would be the ones of the regular election,[70][71] and that the special election would appear after the regular election on the ballot.[71]

As of 2023, this was the last Senate election in Illinois won by a Republican.