In most states Republicans have seen better early-voter turnout than Democrats, but experts warn that the numbers can be deceiving.

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POLITICO examined early voting polls in 20 states, and in 14 of the 15 that allow voter registration by party, Republican turnout is "running ahead of the party's share of statewide voter registration -- whether measured against 2006 or 2008, when President Barack Obama's campaign led to a surge in Democratic voter registration."

Republicans hope to mimic the success Democrats saw in 2008, when huge numbers of early voters turned up to the polls to support Obama.

But Democrats have not lost hope. Many point to states like Iowa and West Virginia, where Democrats are dominating early voting.

Experts agree that early voting statistics can be misleading because states use different systems to track votes, and benchmarks to measure how well Republicans are doing can be subjective.

Nate Silver of The New York Times questioned how Republican success should be measured this year. Should it be compared to the major enthusiasm spike among Democrats in the 2008 elections or against statistics from years prior, where early voting was mostly limited to older (mainly Republican) voters?

In California, officials have not released voter turnout by party, but one private Democratic consulting firm called the Atlas Project reports that Democrats have made up 43 percent of early voters, while Republicans have made up to 39 percent. But registered Democrats outnumber registered Republicans in the state by 44 percent to 31 percent, so early-voting Republicans are outpacing their liberal counterparts.

A state-by-state breakdown of early voting collected by Professor Michael McDonald at George Mason University gives the numbers advantage to the Republicans, but just because a voter is registered under a certain party does not mean he or she will vote for that party's candidate.

In West Virginia, for example, 55 percent of voters have been Democrats, but they could be voting for a candidate other than Gov. Joe Manchin in the Senate race.

Reach associate news editor Taylor Freitas here. Follow her on Twitter: @taylorfreitas.

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