Sen. Richard Lugar (R-Ind.) raised $842,000 in the last three months, his campaign announced Wednesday afternoon.

Lugar faces a tough primary challenge from Indiana Treasurer Richard Mourdock, who is running as a Tea Party conservative. The longtime senator has $3.8 million cash on hand, with $3.2 million available for the primary, a deep but not invincible warchest.

Mourdock has struggled so far with fundraising and had only $214,000 cash on hand at the end of July. He has not yet released his latest fundraising totals, but a source close to his campaign said that part of it will include a $100,000 loan from Mourdock to his campaign.

Lugar, the most senior Republican in the Senate, has not faced any real competition in decades. He did not face major-party opposition in 2006, and the last time he was held to under 60 percent of the vote was in 1982.

But he angered some conservatives by voting for the Troubled Asset Relief Program (TARP), which has been characterized as a Wall Street bailout, and voting to confirm both of President Obama's Supreme Court nominations. Lugar has also backed the DREAM Act, a measure favored by the administration which would give some illegal immigrants brought here as children a path to citizenship.

Mourdock has the backing of some Tea Party groups in Indiana and Washington, D.C. including Hoosiers for a Conservative Senate, Tea Party Express and Citizens United. Freedomworks has scheduled an announcement to endorse him soon, while the Club for Growth has been on the attack against Lugar and may endorse Mourdock as well.