Richard Mourdock defeats Sen. Dick Lugar in Indiana

Click image to see more photos. (John Terhune/Journal & Courier via AP)

Dick Lugar, the longest-serving Republican in the Senate, was defeated Tuesday as Indiana Republicans chose state Treasurer Richard Mourdock over Lugar as the party's nominee.

Mourdock received about 60 percent to 40 percent for Lugar in the Hoosier state's Senate primary, marking a huge win for tea party supporters and conservatives across the country.

Mourdock, speaking at a victory rally in Indianapolis Tuesday night, said that many supporters who joined up with the tea party or other groups wondered at the beginning of his campaign if they could "do the impossible." "Tonight, you did," he said, to wild applause.

Mourdock, who was visibly emotional throughout his speech (notes for which he said he accidentally left at his apartment) asked the audience to honor his opponent, a man he said was never his "enemy."

But Mourdock quickly turned his attention to the general election, accusing his new opponent, Rep. Joe Donnelly-- who ran unopposed in Tuesday's Democratic party-- of being too cozy with President Obama and "that won't be accepted by Hoosier voters."

"The race ahead is going to be hard," Mourdock conceded, but he added that he's already received the support of the National Republican Senatorial Committee.

Conservatives had long targeted Lugar for defeat, arguing he represented a Republican establishment in Congress that has acquiesced to the Democratic party. They singled out Lugar's votes for the bailouts, in support of the president's stimulus and votes to confirm U.S. Supreme Court nominees Elena Kagan and Sonia Sotomayor as evidence of his "RINO" (Republican in name only) status.

National tea party groups such as FreedomWorks and the Tea Party Express as well as the state group Hoosiers for a Conservative Senate and others mobilized and invested in the race, casting the contest as a nationally significant battle to restore conservatism and hold leaders of the Republican establishment accountable.

"Richard Mourdock's historic underdog victory is proof that grassroots activists, armed with good ideas and hard work, can fundamentally change the Republican Party from the inside out," FreedomWorks President Matt Kibbe said in a statement Tuesday night. "This is just one more example of the hostile takeover of the Republican Party that we've been working on since 2009."

Sarah Palin, Michele Bachmann and Rick Santorum were among the high-profile politicians who offered public support for Mourdock's campaign.

Lugar began the race with a major fundraising advantage and drew support from his extensive political network, which led to endorsements from the state's popular governor, Mitch Daniels, and fellow foreign policy expert Sen. John McCain.

The senator congratulated Mourdock in his concession speech Tuesday night and expressed support for Mourdock's candidacy and for Republicans to win back a majority in the Senate. Lugar said Tuesday night that he hopes Mourdock "prevails" in November.

Lugar had been pressed in recent weeks by the Mourdock campaign and others to offer preemptive support to Mourdock pending his primary victory, but Lugar's camp had refused comment.

Lugar's concession speech, issued at a rally held at his Indianapolis headquarters, maintained an upbeat tone with Lugar telling his supporters: "I remain optimistic about the future of Indiana and the United States of America."

In the race's last days, Lugar pivoted from arguing that Mourdock was inexperienced and flawed to branding himself as his party's best hope of defeating Donnelly in the general election in November.

"Democrats understand Joe Donnelly will beat Richard Mourdock," Lugar wrote in an email message to supporters Sunday. "This is serious. Losing our Indiana Senate seat to the Democrats is not a risk that Republicans can take."

Democrats view Lugar's loss as their best chance of capturing the seat, preferring to go up against a newcomer who spent the primary marketing himself to the far right instead of facing a longtime lawmaker who boasts support from independents and Democrats in the state.

Update 10:50 PM ET: This piece has been updated to reflect the latest vote count.

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