Sen. Elizabeth Warren's support among black voters is down to 4% in a new poll, a result that will be deadly to her presidential ambitions if she can't turn things around.

The big news in the new Quinnipiac poll is that Sen. Kamala Harris, at 20%, has surged into a statistical tie with Joe Biden, who is at 22%. Before Harris mauled Biden in the first Democratic presidential debate, Biden was at 30%, and Harris was at just 7%.

One other consequence of Harris' spike is that it came at a time when Warren had been slowly and steadily ascending toward second place. Warren didn't lose much ground overall (she's now at third place, at 14%, instead of at 15%), but Harris's big debate allowed her to leapfrog over Warren.

An area of particular concern for Warren should be her performance among black voters, who make up a key constituency within the Democratic primaries. In 2016, it was the inability of Sanders to win over black voters that destroyed his chances of winning the nomination.

In the poll taken earlier in June, Warren had clawed her way up to 11%, or third place, among non-whites.

But after the debate and Harris surge, Warren is down to 4% — in fifth place among the crucial group.

Interestingly, Sanders is not only beating Warren handily among black voters, but he's actually doing better among black voters than whites, 16% to 11%.

Among some other takeaways from the poll:



This is a bad poll for Sanders overall, as he slipped from second place to fourth — behind Biden, Harris, and Warren.

Harris has made gains across the board and is now even tied with Sanders among self described "very liberal" voters, at 21%. Warren now leads this group with 27% of the vote, although that's down from the 29% she had with the group in the previous poll.

Pete Buttigieg has lost half his support, and is now down to 4% overall, with zero support among black voters. Whether he makes a comeback or not after his impressive fundraising haul is an open question, but for now, his initial boomlet has ended.

Beto O'Rourke is down to 1%. It's much harder to see what his path is back into relevance.

Cory Booker is at 3%. That's up from the 1% in the previous poll, enough to help him qualify for the second round of Democratic debates if he can maintain at least this level of backing. Staying alive in a crowded field is something. But clearly he was unable to capitalize on Biden's stumbles on race as much as Harris, even though he tried to get there first.