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.

With 37 percent reporting, Mourdock received 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.

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.

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 Democratic Rep. Joe 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."

Donnelly ran unopposed for his party's nomination Tuesday.

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.

This definately gives the Democrats a better chance of getting the seat. He is a fringe candidate like Ron Paul, Sharron Angle and Christine O'Donnell.