Donald Trump continues to lead the GOP presidential field, with 25 percent support among Republicans nationwide, according to a Quinnipiac Poll released Thursday. Retired neurosurgeon Ben Carson is close behind at 17 percent, former technology executive Carly Fiorina is at 12 percent, former Florida Gov. Jeb Bush is at 10 and Florida Sen. Marco Rubio is at 9 percent. The other 10 GOP candidates are at seven percent or below.

The results track roughly with a Fox News poll released Wednesday evening that found Trump in the lead at 26 percent, Carson at 18 percent, Fiorina and Rubio at nine percent, Texas Sen. Ted Cruz at eight percent, Bush at seven and the rest below five percent.

And a Bloomberg survey released Thursday also found Trump atop the GOP pack, with 21 percent, Carson trailing him with 16 percent, and Bush in third with 13 percent.

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On the Democratic side, former Secretary of State Hillary Clinton is ahead of Vermont Sen. Bernie Sanders, 43 to 25 percent, according to Quinnipiac. Vice President Joe Biden comes in at 18 percent - less than the 25 percent he received in a Bloomberg poll released yesterday - and the rest of the field receives zero percent.

Similarly, the Fox poll has Clinton at 44 percent, Sanders at 30 and Biden at 18 percent. The rest are at 2 percent or less.

Many recent national polls of the 2016 race reflect a similar trend in both parties: frontrunners who have seen their lead erode in recent weeks.

On the Republican side, Trump's bombastic style hasn't been enough to contain the rise of other "outsider" candidates like Carson and Fiorina. And on the Democratic side, the scrutiny over Clinton's email server, combined with some diminished favorability ratings, have created an opening for Sanders, who's challenging Clinton from the left, and Biden, who's not yet decided whether to run but is consulting prominent Democrats about the race.