Indiana state Treasurer Richard Mourdock raised $875,000 in the last three months for his Senate campaign, more than double what he's brought in during any previous fundraising quarter and significantly more than Sen. Dick Lugar (R-Ind.) raised.

Lugar raised $820,000, a strong haul, and maintains a big cash advantage over Mourdock with $2.5 million in the bank to Mourdock's $430,000. But Mourdock's fundraising haul is the latest sign he has some momentum in the race.

Still, Mourdock will be outspent by the groups that are supporting him — in a big way. The Club for Growth has already spent more than $600,000 on the race, according to a recent Federal Election Commission filing, and the National Rifle Association is already into the hundreds of thousands of dollars.

On the other side, the American Action Network, which backs establishment Republicans, is spending more than a half-million dollars defending Lugar.