It’s the second poll in five days to show her losing ground after the debate, a fate no other candidate has suffered. Virtually everyone else is right around where they were before the debate happened (with one notable exception, which we’ll get to). Only Harris has taken a hit.

Was it because of the exchange with Tulsi Gabbard over her criminal justice record in California? My new hot-take theory is that Gabbard is working deep undercover for the Trump campaign, on a mission to terminate Harris’s candidacy with extreme prejudice. If she’s successful, Secretary of Defense in Trump’s second term.

I base that on absolutely no evidence, I should stress, except for the fact that we live in a reality-show simulation now and that would be a simply awesome second-term plot twist. It’s crazy, therefore it’s probably true.

Anyway, it’s still Grandpa Joe’s race to lose, notes Quinnipiac. And unlike a month ago, it’s not Harris to whom he’s most likely to lose it.

Biden: Steady. Bernie: Steady. Beto: Steady. Buttigieg (not pictured): Steady at five percent. Booker: Steady, unfortunately for him despite his best efforts to beat Biden up at the debates. It’s only Officer Harris who’s lost ground, with nearly half of her support drifting away. She also lost ground in last week’s Morning Consult poll, another survey that showed the rest of the field basically frozen in place. No one seems to have suffered from their performance at the second debate except for the senator from California.

The big difference between this poll and Morning Consult’s numbers is the notable exception I mentioned up top: Elizabeth Warren seems to have picked up Harris’s wayward supporters and now clearly occupies second place in the field. She pulls 40 percent of “very liberal” voters in this poll compared to just 20 percent for her progressive rival, socialist Bernie Sanders. She’s far ahead of Harris among women Democrats, pulling 24 percent to earn second place to Biden. She was also the easy winner in this survey when people were asked who did the best job at the recent debates, pulling 28 percent compared to just 15 for Biden, the next highest candidate. She now leads the entire field among college-educated Dems with 28 percent of that vote; by comparison, Biden leads her handily among Dems without a college degree, 38/26. “Gonna be hearing a lot of wine track/beer track punditry if this holds up,” said Ross Douthat about that divergence.

Back to Harris, though. On July 9, fresh off the first debate, she was in second place in the RCP poll of polls at 15 percent, narrowly ahead of Sanders and Warren. A month later she’s in fourth at 9.3 percent and trending downwards while Sanders and Warren are each in the mid-teens. (Combine Sanders’s and Warren’s totals and they’d be a hair ahead of Biden, a warning sign to Joe that he’s benefiting from an early split field here.) Why is Harris sliding? Pretty simple, really, per Quinnipiac. Note black voters:

Harris and Cory Booker are complete nonfactors among black Dems, pulling a combined one percent of that vote. That’s a devastating result given that each of their strategies hinges on wooing black voters from Biden, particularly in South Carolina. Not only did their attacks on him at the second debate not help them with that but Harris appears to have lost ground after making some inroads with black Dems in polling after the first debate. The lesson seems unmistakable: Attacking Biden for Obama’s policies at the debate backfired, inadvertently reminding Dems of a politician they love. I bet we won’t hear another word from Harris or Booker anytime soon about their issues with Obama-era policies. Only Biden’s pre-O Senate record will be targeted from now on.

The other key to Biden’s lead comes from the numbers when Dems are asked who’s most likely to beat Trump. No contest:

Democratic voters are even more likely now to say that they value electability in a nominee over agreement with them on the issues, rising from 45 percent in March to 50 percent now. So long as Biden looks like he’ll give Trump the toughest time, he’ll get the benefit of the doubt from swing voters.

As for Gabbard and America’s sweetheart, Marianne Williamson, they’re nowhere here despite their standout debate performances. Gabbard is at one percent and Williamson is an asterisk. They didn’t even do well on the question of who performed best at the debates, with Gabbard pulling three percent and Williamson two. Democratic voters seem pretty bottom-line about this race: Just win. Muttering about “dark psychic forces” is fun but doesn’t get them closer to the end zone of ousting Trump.

Exit question via Nate Cohn: Should billionaire impeachment fanatic Tom Steyer be included in these national polls? He’s been spending money on advertising in early states and, er, he’s right on Harris’s heels for entry into the top tier.