President Obama's uphill battle to re-election is getting steeper.

A report released today by the centrist think-tank Third Way showed that more than 825,000 voters in eight key battleground states have fled the Democratic Party since Obama won election in 2008.

"The numbers show that Democrats' path to victory just got harder," said Lanae Erickson, the report's co-author. "We are seeing both an increase in independents and a decrease in Democrats and that means the coalition they have to assemble is going to rely even more on independents in 2012 than it did in 2008."

Amid frustrating partisan gridlock and unprecedentedly low party-approval ratings, the number of voters registering under a major party is falling fast, but it is also falling disproportionately.

In eight states that will be must-wins in 2012 - Colorado, Florida, Iowa, Nevada, New Hampshire, New Mexico, North Carolina and Pennsylvania - Democrats lost 5.4 percent of their registered voters while Republicans lost 3.1 percent. The number of independent voters in those states jumped 3.4 percent.

"People are frustrated and the way you tune out in American politics is that is you drop the label of the two parties," said Steven Jarding, a Harvard public policy professor and Democratic campaign strategist. "The danger for Obama in this is he is not only going to have to capture them but capture more of them because there are less Democratic voters."

There will likely be more independent voters in the upcoming election than there has been in nearly 50 years, according to the report. But Jarding argues that could actually help Obama, if he plays his cards right.

"On paper, it looks like, 'Well, it's just going to be bad for Obama,' but a part of me says, 'Bad in what sense?' He's proven that he can get independent voters," Jarding said.

Obama snagged 52 percent of unaffiliated voters in 2008, but those independents flocked to Republicans in the 2010 midterms with 56 percent opting for a GOP candidate. Between 2008 and 2010, there was a 27-point shift in which party independents chose.

"Independent voters have been the deciding factor in the last two major elections," said Omar Ali, spokesman for IndependentVoting.org. "And they are going to, more than likely, determine the 2012 presidential election."

Obama's campaign team has already launched two get-out-the-vote initiatives in the hopes of re-creating the web of grassroots support that propelled him into the White House.

The Obama re-elect machine kicked off Project Vote  this summer, a targeted voter outreach program aimed to boost minority registration, and the website, GottaRegister.com, which offers interactive online voter registration on desktops, laptops, tablets and mobile devices.

Harvard's Jarding said the unprecedented increase in independent voters "fundamentally changes" how candidates have to run their campaigns. Instead of convincing a list of party voters to turn out to the polls, candidates now have to build "much stronger" grassroots efforts to interact with undecided voters.

"People are very, very disillusioned and the danger for Obama is when people are disillusioned  and when they are hurting they tend to throw the guy in power out," Jarding said. "If Obama can't turn out the vote that he did in 2008, he's in trouble."

Ali said that while candidates mobilize their party's base by talking about ideology, they will have to focus on bipartisanship in order to make their case to independents.

"What [Obama] needs to do is present himself as somebody above partisan politics," IndependentVoting.org's Ali said. "Independents, in some ways they span the ideological spectrum. The one thing they agree on is having a more open and transparent political process."