A new poll of possible 2016 presidential contenders shows a crowded Republican field while former Secretary of State Hillary Clinton has a wide lead on the Democratic side. No potential GOP candidate received more than 20 percent support in the Quinnipiac University Poll released Thursday morning, but the 56 percent support Clinton garnered is four times as great as her nearest rival, U.S. Sen. Elizabeth Warren, D-Mass.

Wisconsin Gov. Scott Walker and former Florida Gov. Jeb Bush are competing for front-runner status among Republicans, with Walker topping the poll at 18 percent and Bush not far behind at 16 percent. They were followed by New Jersey Gov. Chris Christie and former Arkansas Gov. Mike Huckabee at 8 percent each, retired neurosurgeon Ben Carson at 7 percent; and U.S. Sens. Rand Paul, R-Ky., Marco Rubio, R-Fla., and Ted Cruz, R-Texas, with 6 percent apiece.

Clinton is the clear favorite among Democrats. She received 56 percent in the poll compared to 14 percent for Warren, 10 percent for Vice President Joe Biden and 4 percent for independent Vermont Sen. Bernie Sanders. About a quarter of Democratic-leaning voters were undecided.

"It's Gov. Scott Walker and former Gov. Jeb Bush head-to-head for the GOP and Hillary Clinton virtually unchallenged among Democrats. Her 4-1 margin over Sen. Elizabeth Warren and 5-1 lead over Vice President Joseph Biden say it's hers if she wants it," Tim Malloy, assistant director of the Quinnipiac University Poll, said.

Clinton also leads every potential GOP candidate in head-to-head matchups. She has the smallest margin against Bush, whom she leads 45 percent to 42 percent. She has the largest lead against Cruz, 48 percent to 38 percent.

The poll was conducted between Feb. 26 and March 2, before it was revealed that Clinton exclusively used personal email to conduct State Department business. It’s unclear if the controversy will affect Clinton’s poll numbers going forward.

The poll surveyed 1,286 registered voters. It had a margin of error of plus-or-minus 4.4 percentage points.