A wide swath of party financiers is already convinced that Biden will make a late entry into the race and a sizeable number are now contemplating backing him, including some who have already signed on with Clinton, according to more than a dozen top Democratic fundraisers around the country.

Their potential support — driven in part by a desire to recapture the passion they felt in Obama’s campaigns — could play a key role in helping the vice president decide whether to move forward on a third White House run.

Clinton still maintains a deep and loyal donor base, and her financial dominance would present a huge challenge for Biden if he entered the campaign this fall. The former secretary of state amassed a record $47 million during her first quarter as candidate, and is flanked by an array of super PACs and other independent allies socking away millions to help her secure the presidency.

But there is growing unease among some of Obama’s biggest financial backers about the controversy over Clinton’s use of a private e-mail server while she was secretary of state, providing an opening for the vice president.