Elizabeth Warren should be ready for Democratic critics to dredge up her claims of Native American heritage — if not on stage during the Iowa debate, then at least online during the closing weeks of the primary.

Less than three weeks out from the first-in-the-nation caucuses on Feb. 3, the Democratic race’s once collegial tone has deteriorated into dirtier mudslinging. The transition coincides with the top four candidates for the 2020 presidential nomination, Joe Biden, Pete Buttigieg, Bernie Sanders, and Warren, swapping the lead in a slew of recent polls coming out of the state.