Heading into the 2012 election, Republicans appeared to have the edge among big money groups and Democrats were sounding the panic button.
But in hindsight, pundits say Republicans are the ones on the losing end of big spending by outside groups.
In the Republican presidential primary, Super PACs extended the primary season and kept candidates like former House Speaker Newt Gingrich and former Pennsylvania Sen. Rick Santorum on life support.
Primaries have always forced candidates from the center, but the 2012 Republican primary went on so long that pundits say Romney, the eventual nominee, lost momentum with independents he never recovered.
"It forced Mitt Romney to be very conservative for longer and forced him to run to the right so he wouldn't be outflanked by his opponents," says Anthony Corrado, a campaign finance expert at the Brookings Institution.
Outside groups like Santorum's Red, White and Blue Fund and Gingrich's Winning Our Future spent millions beating up on eventual GOP nominee Romney, attacking his conservative credentials so much in the primary that it took Romney time to solidify his base even after he won the nomination.
"He didn't get that surge of support in April and May that one would expect for the nominee of the party," Corrado says.
And in key Senate races, big money damaged the GOP.
In Indiana, groups like Club for Growth Action, a conservative PAC, spent nearly $1 million in the state's Republican party primary to defeat three-decade incumbent Sen. Dick Lugar. In a general election, $1 million might be loose change, but in a primary, experts agree it makes a major splash. Club for Growth threw its support behind tea party candidate Richard Mourdock early, but he proved to be a liability. Right out of the gate, Mourdock gave Indiana's moderate Republicans pause when he said he thought compromising in the Senate would happen when Democrats agreed with Republicans.
"I don't think there's going to be a lot of successful compromise," Mourdock told CNN. "I hope to build a conservative majority in the U.S. Senate so bipartisanship becomes Democrats joining Republicans to roll back the size of government."
The state's Democratic Senate nominee Joe Donnelly played up Mourdock's conservative roots in campaign ads and when Mourdock said "even when life begins in that horrible situation of rape, that it is something that God intended to happen," that helped Donnelly win by 5 points.
"In Senate races where Republicans have nominated very conservative candidates, they've had a very difficult time winning," Corrado says. "Once they emerge onto the statewide stage, it becomes increasingly clear with everything they say that they are more conservative than the electorate."
But Matt Hoskins, executive director for Super PAC Senate Conservative Fund, says that it wasn't outside groups who caused the GOP to lose Indiana's Senate race, it was fellow Republicans who turned on Mourdock after his gaffe.
"Republicans could have won that seat after the primary," Hoskins says. "It was the attacks against [Mourdock] from his own party that hurt him. They threw him under the bus."
In Missouri, however, conservative Super PACs didn't pick the most extreme candidate in the race. Democrats did.
Democrats used a competitive, three-way Republican primary to get behind Christian conservative Todd Akin. Democratic Super PACs dumped $1 million to help Akin, the candidate who polled the worst against their incumbent Democratic Sen. Claire McCaskill. And it worked. Majority Pac, a Super PAC whose mission is to maintain a Democratic majority in the Senate, poured $1.2 million into the race to tear down the front-running, competitive Republican primary leader, all in an effort to prop up Akin in the race.