Will Joe run? It’s the biggest unanswered question hanging over the Democratic primary. The vice president is making some of the traditional campaign stops (late night talk shows, parades and speeches), but he sometimes sounds like a man who’d rather sit this one out.

How would a Biden run affect the race? Being a hypothetical candidate is easier than being a real candidate — just ask Fred Thompson — so the early polls that include Biden can’t tell us much. But they still hold a couple of clues: Even as a hypothetical candidate, Biden is eating into Hillary Clinton’s support, and black voters, in particular, appear open to him.

Four national polls released this month (ABC News/Washington Post, CBS News/New York Times, YouGov and CNN/ORC) asked Democratic voters who they’d vote for with Biden in the race and without him. Clinton led Bernie Sanders by an average of 44 percent to 26 percent with Biden in the race. Clinton’s 19-percentage-point edge in those polls equals her lead in the Huffington Post/Pollster aggregate. Without Biden, Clinton’s lead on Sanders jumps to 28 percentage points, 57 percent to 29 percent.

In other words, almost all of Biden’s support is coming from people who, without Biden in the race, would support Clinton. So if Biden decides not to run, Clinton’s standing could snap back to where it was earlier this year.

In fact, if you look only at polls that don’t include Biden, Clinton’s margin over Sanders hasn’t changed all that much in the past couple of months. Clinton averaged a 30-percentage-point lead in such polls in August; she’s averaged a 28-point edge in them so far in September.

Still, there are a few rays of hope for the Sanders camp in these numbers, even if Biden doesn’t enter the race.

In the ABC News/Washington Post survey, Clinton’s lead among non-white voters — a group Sanders has so far failed to make any inroads with — goes from 44 percentage points over Sanders with Biden in the race to 59 percentage points over Sanders without Biden. With whites, she goes from being down 2 percentage points to Sanders to being up 2 points — a minimal difference.

Neither Iowa nor New Hampshire has a lot of non-white voters, so to win those states Sanders doesn’t need Biden drawing away Clinton supporters. The most recent Des Moines Register poll in Iowa had Clinton ahead by 7 percentage points with Biden in the race and by 8 points without him. Quinnipiac had Clinton down 1 percentage point with Biden running in Iowa and up 3 points without him. Monmouth had Sanders up 7 percentage points in New Hampshire both with and without Biden.

If Sanders wins in Iowa and New Hampshire, perhaps his victory would throw the whole race into enough turmoil that non-white voters would give him another look. Of course, it’s also possible Clinton would hold onto her large lead among non-white voters and easily win the contests in the more diverse states that follow, Nevada and South Carolina.

Either way, Biden’s strength with non-white voters, and specifically black voters, suggests they could be peeled away from Clinton under the right circumstances. Given that Sanders is still fairly unfamiliar to black voters, maybe he can improve his standing with them. The potential problems for Sanders: Minority voters are closer to Biden and Clinton ideologically, and Sanders’s reception among African-American crowds hasn’t been all that enthusiastic.

A Biden run would be bad news for Clinton. He can reach party actors and voters that Sanders hasn’t been able to win over so far. And the hypothetical Biden candidacy has exposed some soft spots in Clinton’s support. Still, Clinton maintains a lead in the polls and the endorsement primary that’s better than Al Gore’s was at this point in the 2000 campaign, and Gore went on to win every single primary and caucus.