As the fight for the GOP nomination moves  to New Hampshire this week, the six remaining Republican candidates are picking up their phones, loading up their planes and filling up their email outboxes to convince supporters to hit the "donate" button and help refill their war chests.

Iowa, despite its relatively small population and inexpensive media markets, did a number on candidates' campaign cash. Mitt Romney and Rick Santorum both spent at least $1 million campaigning in the Hawkeye State.

But it was Super PACs,  independent groups that can spend unlimited amounts of money to support any candidate, that did the financial heavy lifting.

Romney's Restore Our Future Super PAC doled out $4.6 million in Iowa, almost all of which was used on television ads attacking Newt Gingrich, who fell from the top of the polls to finish fourth in Tuesday's caucus.

"Money matters, and you saw it with the way Mitt was able to bring Newt down several pegs," said Norman Ornstein, a political scholar at the American Enterprise Institute. "If hadn't been for the $4 million in ads against Newt, he would have been right up there with others, so it's not like money isn't relevant."

The independent group supporting Santorum - who two weeks ago was polling around 3 percent - spent a small fraction of that amount, about $400,000.

But where the first-in-the-nation state taketh away, Iowa caucus momentum giveth forth.

Riding high on his near-win in the Iowa caucuses, Santorum boasted bringing in $2 million in the 48 hours following Iowa's voting - doubling the amount his campaign had raised before the first nominating contest. And that funding trajectory seems to be continuing.

"It's a reality of his candidacy," said Thomas Mann, a political scholar at the nonpartisan Brookings Institution. "Until he managed to play strongly in Iowa, he was largely considered a joke and simply unable to raise money.  Now it's flowing in, but it may not last."

With his newfound funds, Santorum is making a play for South Carolina next week that includes a "major" cable television ad buy, a direct mail campaign and hiring additional staff, aides confirmed to ABC's Jake Tapper on Thursday.

As  for Santorum,  the sixth GOP contender to balloon to the top of the polls,  Mann said the odds were the  funding stream could dry up quickly if  he does not place well in the remaining January primaries.

"We have had a lot of people do well in Iowa and then flame out, and he could be one of those," Mann said. "He may be the fifth or sixth in line of not-Romney candidates, who have risen quickly and then descended even more precipitously."

Ron Paul, who finished a close third in Iowa, is also using his top-tier showing to raise serious cash.

The Paul campaign said today that it raised $13 million in the fourth quarter of 2011, a total only Romney is expected to exceed. The former Massachusetts governor's campaign said he brought in $20 million in the final months of 2011.

Paul, with 18 percent support,  is currently in a distant second place in New Hampshire behind Romney's 41 percent, according to a Suffolk University/7News poll released Thursday.

The three-time presidential candidate's Super PAC swooped into the Granite State Thursday, announcing a "six-figure" television ad buy to run next week, including three spots that will run during the ABC News/Yahoo!/ WMUR debate Saturday night.

While Republican fundraisers and super PAC spending is hogging the majority of the spotlight, Democrats aren't sitting on the sidelines of this money game.

The Democratic National Committee, which raises and spends money to support Democratic candidates - including the president - for  federal office, raised $6.7 million in November, the last month for which data is available, and had slightly more than $6 million cash on hand as of Nov. 30.

But those numbers pale in comparison with Republicans' reported fundraising. In the month of November, the Republican National Committee took in more than $13 million and ended the month with about $7.2 million cash on hand.

Compared to the president's, both committees' totals are peanuts. In the first nine months of 2011, Obama raised more than $88 million for his re-election. Compare that to the $32.6 million that Romney brought in or the mere $1.3 million that Santorum raised from January through September.

"Obama will not be at a financial disadvantage in this election," Mann said. "He will rasie all the money he needs to run the campaign he wants to run."

ABC News' Shushannah Walshe, Elizabeth Hartfield,  Jake Tapper and Michael Falcone contributed to this report.