Former Secretary of State Hillary ClintonHillary Rodham ClintonDebate organizer questions moderator factchecking Sanders discourages third-party votes: 'Not the time for a protest vote' Trump adviser: Polls show public starting to 'really wake up' MORE (D) remains the clear front-runner for the Democratic presidential nomination in 2016, while New Jersey Gov. Chris Christie (R) narrowly leads a packed field of GOP contenders, according to a CNN-ORC poll released Monday.
Biden headlined a high-profile Democratic fundraiser in the early caucus state of Iowa on Sunday, and political watchers are debating whether the vice president would challenge Clinton in the Democratic primary if she were to decide to run.
The Republican field is far more crowded. Christie leads at 17 percent, just edging Rep. Paul RyanPaul RyanRyan has 'no idea' who will win election Sunday shows preview: Both sides gear up for debate FULL SPEECH: Obama celebrates African American museum opening MORE (R-Wis.) at 16 percent. Ryan was the Republican vice presidential candidate in 2012.
Sen. Rand PaulRand PaulSaudi skeptics gain strength in Congress Senators challenge status quo on Saudi arms sales Five tips from Trump's fallen rivals on how to debate him MORE (R-Ky.) came in third at 13 percent, followed by former Florida Gov. Jeb Bush (R) at 10 percent, Sen. Marco RubioMarco RubioSenate rivals gear up for debates Rubio: End of Obama's term could be 'most damaging yet' Fifteen years since pivotal executive order, STORM Act could help fight terror finance MORE (R-Fla.) at 9 percent, Sen. Ted CruzTed CruzPence offers Cruz 'heartfelt thanks' for Trump endorsement Cruz: Trump hasn't apologized for personal insults Cruz says he forgives Trump for attacks on family MORE (R-Texas) at 7 percent and former Sen. Rick Santorum (R-Pa.) at 5 percent. Santorum was the foremost challenger to Mitt Romney for the 2012 Republican presidential nomination.
Clinton and Christie are two of the most popular political figures in the country, and both routinely register strong favorability ratings in public opinion polls. One Quinnipiac University poll from last month showed Clinton edging Christie 46 to 40 in a head-to-head match-up.
None of the potential candidates have publicly committed to a 2016 run. However, Ready for Hillary, a super-PAC pushing the former New York senator to run, is loaded with former Obama campaign activists.
The CNN-ORC poll of 1,022 adults was conducted between Sept. 6 and Sept. 8 and has a 4.5-percentage-point margin of error.