Former Vice President Joe Biden is tied for the lead with Sen. Bernie Sanders (I-VT) in Iowa, according to a new online survey conducted by the Democratic firm Change Research.

Biden and Sanders both sit at 24% support among likely caucus-goers, according to the survey, with South Bend Mayor Pete Buttigieg (D), at 14%, Sen. Elizabeth Warren (D-MA) at 12%, and Sen. Kamala Harris (D-CA) at 10%, according to the survey. No other candidate was higher than 5% in the poll.

This survey suggests a wide-open race for the Democratic nomination — and numbers that could be problematic for Biden as he looks to maintain his front-runner status. The former vice president might have a big lead in national polls, but the early-voting states of Iowa and New Hampshire matter the most in terms of how the race will actually shape up since they go first.

A few caveats: Change Research’s online polling methodology isn’t the live-caller phone polling favored by top pollsters, and while the pollster had fairly accurate polling in the 2018 midterms, their track record is relatively limited compared to some longtime pollsters. The survey of only likely voters also might be too tight a measure of who will actually vote this far out from the Iowa caucuses.

But Biden’s huge national lead appears to be considerably slimmer in both Iowa and New Hampshire with more than six months until the primaries and caucuses — if it exists at all.

There haven’t been any other recent polls of Iowa Democrats. An early April Monmouth University poll, conducted before Biden had announced his campaign, found Biden with an 11-point lead over Sanders, while a late March Emerson poll had Biden and Sanders essentially tied.

Change Research conducted the online poll of 615 likely caucus-goers for Iowa Starting Line from May 15-19. It has a margin of error of 3.9%.