Republican Senator Richard Lugar is battling for his political survival against a Tea Party-backed GOP challenger in Tuesday's Indiana primary, and the face of Indiana politics for almost four decades is likely to be defeated.

Polls in Indiana signaled momentum for Indiana Treasurer Richard Mourdock, but Lugar is still clinging to hope that a large turnout may propel him to victory. 

"If they come, we will win," Lugar said.

PolicyMic will be live blogging the Indiana primary. Polls close at 7:00pm EST. Refresh this page for live updates.

UPDATES: 10:00 PM Sen. Dick Lugar released two concession texts tonight. In the first he wrote, "I also advanced several propositions that were considered heretical by some, including the thought that Congressional earmarks saved no money and turned spending power over to unelected bureaucrats and that the country should explore options for immigration reform.

It was apparent that these positions would be attacked in a Republican primary. But I believe that they were the right votes for the country, and I stand by them without regrets, as I have throughout the campaign."

In the second, he said, "Hoosier Republican primary voters have chosen their candidate for the U.S. Senate. I congratulate my opponent on his victory in a hard fought race. I want to see a Republican in the White House, and I want to see my friend Mitch McConnell have a Republican majority in the Senate. I hope my opponent prevails in November to contribute to that Republican majority." This is the final update of the evening.

9:25 PM 83% now reporting. Mourdock 60.6% vs. Lugar 39.4%. Politico headline: "Lugar routed."

8:23 PM Numbers update: 60% reporting: Mourdock 60.1% vs. Lugar 39.9%. Romney 64.3% and Paul 15.2%.

8:20 PM Reactions on Twitter:

The Tea Party is alive and well as shown by the defeat of @dicklugar a 36 yr establishment hack!Good riddance!

— David Spielman (@SpielzOnWheels) May 8, 2012 

I was just handed a copy of @dicklugar's concession speech. He says he hopes @richardmourdock wins in November. #INSen

— Eric Bradner (@ericbradner) May 9, 2012 

7:53 PM EST BREAKING: Dick Lugar has officially lost Indiana to Richard Mourdock. With 40% reporting, Mourdouck has 60.3% of the vote (189,405) compared to Lugar's 39.7% (124,795). Lugar cannot overcome the deficit.

7:44 PM EST Starting to tighten up in the polls. Reports coming in that Lugar now at 40.2 percent of the vote, trails Mourdock by approximately 50K votes.

7:37 EST: Via Stewart Burns: "Will the sun really come up tomorrow? It seems likely that when I wake up in the morning, once one of the brightest shining leaders in the world, Senator Richard Lugar, will be on his way out of office. The Tea Party, their candidate Richard Mourdock and the millions of dollars coming in from national organization have taken down an icon."

7:32 EST: With 20% reporting, Mourdock leads by a wide margin: 60.8% compared to Lugar's 39.6%.

7:30 EST With 20% reporting, Mitt Romney is on his way to defeating Ron Paul in Indiana by a current total of 64% to Paul's 14.6%

7:15 EST On the ground report from Nick DeBoer, Purdue University Class of 2011

"I live on the campus of Purdue University, and the only Millennials I know who are in favor of Lugar are a small subset of political informed yet moderate leaning individuals. The liberal and conservative activists are both hoping for a Murdock victory. The liberals see a clear path to a Donnelly victory if Murdock is his opponent, and the conservatives think that if they can beat Lugar, it's inconceivable to lose to a three term congressmen.

The press has been reporting this as likely a Lugar loss, mostly on the merit of two polls done in Indiana which only assumed around 2% of the electorate would be lean Democratic.

This may underestimate the electorate, especially when no notable contests exist on the Democratic side. I think tonight may be closer than these polls are anticipating due to their model.

All that being said, the energy of the conservative movement is behind Murdock, but Indiana is not a classical conservative movement state. I can say this with quite a bit of confidence as an individual who worked tirelessly for Obama in 08, but voted for Governor Daniels reelection (mostly due to the weakness of his opponent). The established political forces in this state are Republican, not conservative, and Richard Murdock would be a vivid departure of this political norm. A Murdock win will open the door for the Obama campaign to heavily compete here while trying to hold on to the Senate."

7:10 EST: Reports on the ground: turnout is extremely low, according to sourced inside the city government. This benefits Mourdock.

6:30 EST Latest polls show Lugar is 10 percentage points behind Mourdock. 

Mourdoch is a 60-year-old conservative who's running on the record of change. According to a an anti-Lugar ad: "When Dick Lugar moved to Washington, he left behind more than his house. He left behind his conservative Hoosier values." The 30-second ad says Lugar has been called "Obama's favorite Republican."

BACKGROUND: Lugar is the longest serving Senator in Indiana's history, and he blames his likely exit on the influence of money in politics. "Thank goodness the founder of our country did not face million of dollars of negative advertising," he said. 

Lugar was first elected to the Senate in 1976, but he became the targe of Tea Party groups who argued he no longer represents his constitutents and is too moderate. Lugar's challenger Mourdock says he has become more interested in compromising with liberals in Washington than representing conservatives back home. 

Tea Party groups have spent $4.5 million in negative ads to defeat 80-year-old former Indianapolis mayor.

Other major contests of note are:

* In the 2nd district: Iraq veteran Brendan Mullen (D) faces off against 2010 GOP nominee and former state representative Jackie Walorski (R) this fall.

* In the 8th district, freshman Rep. Larry Bucshon (D) is likely to face former state representative Dave Crooks.