Elizabeth Warren leading Joe Biden in recent Democratic presidential primary polls

Former Vice President Joe Biden's position as the frontrunner in the 2020 Democratic primary seems to be in jeopardy.

Most national polls taken since the end of September have found Sen. Elizabeth Warren of Massachusetts – not Biden – leading the pack, albeit by relatively narrow margins.

Biden had led in almost every national poll, usually by double digits, going back to 2018. But Warren has come out on top in four of the last five, and six of the last 10 of them.

And she recently pulled...