Donald Trump atop in GOP candidate field: poll

U.S. billionaire Donald Trump leads the GOP presidential candidate field by a significant margin, according to a new Quinnipiac University national poll released Thursday.

The poll shows that Trump is on top of the new Quinnipiac poll with 20 percent, Wisconsin Governor Scott Walker is next at 13 percent and former Florida Governor Jeb Bush follows at 10 percent.

The new numbers also show a strong rise by Ohio Governor John Kasich, who announced his campaign just last week. He's more than doubled his support since Quinnipiac's last national survey in late May, which bodes well for his chances to be in the top 10 come the first Republican debate.

Bush's share of the field has remained stagnant since that late- May poll, while Walker had a 3-point uptick.

Despite leading the field, Trump has the worst favorability score among the GOP field, which translates into a poor showing in a head-to-head match-up against Democratic front-runner Hillary Clinton. She'd defeat him by a margin of 48 percent to 36 percent, according to the poll.

In the Democratic primary, Hillary Clinton maintains her wide advantage over Vermont Senator Bernie Sanders, 55 percent to 17 percent, statistically unchanged from two months ago, when Clinton led Sanders, 57 percent to 15 percent.

But there are warning signs for Hillary beyond the primary. Her favorability rating reached an all-time low in the new survey at 41 percent. Fully half of voters now view her unfavorably. Among male voters, only one in three views her favorably while female voters are split on Clinton with 47 percent favorable, 43 percent unfavorable.

Two months ago, similar percentages of all voters viewed her favorably at 45 percent and unfavorably 47 percent. Endite