Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE has passed Hillary Clinton Hillary Diane Rodham ClintonHillicon Valley: FBI chief says Russia is trying to interfere in election to undermine Biden | Treasury Dept. sanctions Iranian government-backed hackers The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters FBI chief says Russia is trying to interfere in election to undermine Biden MORE at the top of a national poll for the first time in the 2016 race.

A Fox News poll of the Democratic presidential race released Thursday shows Sanders with 47 percent support to Clinton’s 44 percent.

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That's a gain of 10 percentage points for Sanders a January version of the poll. Clinton's support declined 5 points.

Clinton posted leads as high as 30 points over the summer, but Sanders has been steadily closing the gap. While no other poll of the race going back to 2014 has ever showed Clinton trailing a rival, she led Sanders by just 2 points in the last two Quinnipiac University tracking polls.

It's unclear whether the numbers are outliers or indicative of a dramatic change in the race. Outside of the Quinnipiac poll, Clinton posted double-digit leads in all three national polls conducted in February, with the largest lead coming in at 21 percentage points.

“One thing that is clear from our poll — and others — is that Clinton has been losing support and Sanders has been gaining,” said Democratic pollster Chris Anderson, who assisted Fox News on the poll.

“And this process appears to have accelerated since the contests in Iowa and New Hampshire.”

Fox released the poll two days before Saturday's caucuses in Nevada, a state where Clinton has also seen a major lead evaporate. A CNN/ORC poll from this week found the White House hopefuls essentially tied there.

The Democratic establishment had long viewed Clinton as the inevitable nominee, but anxiety is growing, with some fearful that the campaign is slipping away from her.

Sanders's lead in the Fox poll comes due to improved numbers among female voters — a net loss of 25 points for Clinton over the past month — and gains among white voters, with a decline of 13 points for Clinton. But the poll shows Clinton still holding her lead with black voters.

The poll also found that a vast majority of Democrats, 72 percent, believe Sanders is "realistic enough" to serve as president despite repeated attacks by the Clinton campaign that his policies on healthcare and subsidized public college tuition are a pipe dream.

There are also signs that Sanders is catching on with the broader electorate.

Thirty percent of all voters would consider themselves satisfied if Sanders wins the White House, more than said the same of Clinton or Republicans Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE or Jeb Bush. Sanders also has the lowest number of people out of those four candidates who would be "not at all" satisfied with his election.

Updated at 6:53 p.m.