Joe Biden is surging - and he has one clear advantage over Hillary Clinton

Vice President Joe Biden would beat several Republican presidential contenders in hypothetical matchups, giving him an advantage over former Secretary of State Hillary Clinton if he were to jump into the race.

Biden, who is still weighing whether to mount a late challenge to the Democratic presidential front-runner, continues to rise in polls of the Democratic primary.

But even though Clinton maintains a significant lead over Biden and Sen. Bernie Sanders (I-Vermont), she is trailing several Republican rivals in hypothetical general-election matchups.

A new poll from Quinnipiac University out on Thursday tested both Clinton and Biden against former Gov. Jeb Bush of Florida, former Hewlett-Packard CEO Carly Fiorina, retired neurosurgeon Ben Carson, and real-estate mogul Donald Trump.

Clinton beats only Trump head-to-head, while Biden is tied with or has somewhat comfortable leads on all four Republican hopefuls.

Here are the results for Clinton:

• Bush 44, Clinton 42
• Fiorina 44, Clinton 43
• Carson 49, Clinton 42
• Clinton 45, Trump 43

And for Biden:

• Biden 46, Bush 41
• Biden 46, Fiorina 43
• Biden 45, Carson 45
• Biden 51, Trump 40

The Quinnipiac survey shows Biden grabbing 18% of the Democratic primary vote nationally if he were to jump in, well behind Clinton's 43%. Sanders gets 25% of the vote. But in a sign of his surge over the past month, Biden has nearly doubled his support in a Fox News poll. That poll also shows Biden as an overwhelming second-choice candidate for Democrats.

There are two key factors to Biden's rise and the slump for Clinton, whose campaign has been bogged down this summer by a slew of stories detailing her controversial use of a private email server as secretary of state.

According to the Quinnipiac poll, Biden has the highest favorability rating of any leading presidential contender, with 50% of voters overall viewing him favorably. He also boasts the third-highest net favorability rating, behind Carson and Fiorina, with only 34% seeing him in a negative light.

Clinton, meanwhile, has a negative 41-55 favorability split. And by the same token, voters say by a 63-32 margin that she is not "honest and trustworthy." By a 62-27 split, voters say Biden is honest and trustworthy - again, he sits only behind Carson in that category.

People close to Biden increasingly believe he will take the plunge and challenge Clinton for the Democratic nomination. NBC's Chuck Todd, citing unnamed sources, reported Sunday that Biden's wife, Jill Biden, is "100%" on board with a potential presidential campaign.

Biden has been criss-crossing the country with vigor in recent weeks, stopping in politically key swing states. He reportedly met recently with one of President Barack Obama's top fundraisers on Wall Street. And a group of prominent Democratic donors circulated a letter Friday urging Biden to take the plunge.