In the Fox News survey, Sanders captured 47% of support among likely Democratic voters nationally. Clinton, who has long been the Democratic frontrunner, garnered 44%.

Though Clinton's lead has shrunk significantly over the past several months, the Fox News poll is the first to show the senator ahead outright.

But it presented a divergent result from other recent surveys. An NBC poll released on Thursday evening showed Clinton maintaining an 11-point lead over Sanders nationally. Still, that represented a 14-point swing from when the same poll was conducted last month, before Sanders' double-digit New Hampshire primary win.