A new CBS News poll shows Joe Biden, Elizabeth Warren, Kamala Harris and Bernie Sanders as the top tier Democratic candidates for the nomination for the 2020 presidential election.

The poll, which is across the early primary and caucus states, shows Biden leading the field with 25%, Elizabeth Warren at 20%, Kamala Harris at 16% and Bernie Sanders at 15%.

“If we consider a 15% threshold as the minimum support needed to win convention delegates, then across the early states, four candidates would meet that benchmark: Biden, Warren, Harris and Sanders.”

The poll also found that the race “is tighter now among estimated delegates across early states, the true measure of the contest — delegates to the convention. By this measure, Warren is much closer to Biden due to stronger showings especially in very liberal areas.”