The political world has been abuzz with rumors that Vice President Joe Biden is eyeing the White House for 2016.

Democrats are split almost down the middle as to whether or not they would welcome such a run, according to Gallup data. An August poll shows that 45 percent of Democrats -- including independents who lean that way -- are in favor of such a campaign, but 47 percent are not.

Biden would have to face off against Hillary Clinton and Bernie Sanders, both of whom have already been on the campaign path with force. A recent poll shows Clinton as the first choice of 37 percent of those who might attend a Democratic caucus in Iowa -- Sanders taking 30 percent.

"Sanders isn't really the issue here," said John Sides, associate professor of political science at George Washington University. "The big person to catch up to is Clinton, and that will be very, very hard to do. She simply has too much support within the party already."At the same time, Sides pointed out, Biden presents more of a threat to Clinton's voting base than to Sanders'.

"Any successful candidate needs to build a fairly broad base of support," he said. "Clinton's is much broader than Sanders', and I think Biden would need to draw from her support among white moderates, blacks, and Latinos."

Biden's challenge is finding a way to appeal to voters that Clinton and Sanders haven't already claimed. Clinton holds sway with the mainstream Democratic Party, while Sanders attracts the far left and young activists.

"I think it would be difficult for Biden to catch up to Clinton or Sanders at this point," said Candice Nelson, professor of government and academic chair of the Campaign Management Institute at American University. "He would be behind in fundraising, and there is no natural constituency that either Clinton or Sanders aren't representing."

Biden does have an attribute that none of his opponents can claim -- serving as vice president during the Obama administration. How that could affect a presidential bid remains to be seen.

"It depends on how popular Obama is going forward," Sides said. "He is very popular among Democrats, but it's not clear whether he'll be popular enough among the general electorate for an association with Obama to be an asset in November 2016."

Much of the vice president's campaign work could be done for him if Clinton falters, a recent Reuters/Ipsos poll shows. More than 38 percent of Democratic responders said they would support Biden if Clinton loses ground, while just 30 percent would side with Sanders.

In any case, time is of the essence. As the clock ticks closer to 2016, Biden has a lot of catch-up to play.

"There is no one hard-and-fast deadline," Sides said. "But he needs to decide soon so that he can begin to raise funds and also ensure that he is on the ballot in all the different primary states."