So far the Sanders response to this swoon has been a kind of base strategy, which seeks to register and mobilize while blunting Warren’s momentum by emphasizing Bernie’s brand as the real left-winger in the race. Hence his big speech explaining democratic socialism; hence his debate performance, conducted at a “we need a revolution, not just a white paper” pitch.

But when you look at the polls of Democrats’ first and second choices, you see something interesting: While there are certainly Warren voters for whom Bernie is a second choice, there are actually more Biden voters who list Sanders as their second option (and vice versa).

This is proof, in part, that voters don’t always fit the neat ideological categories that columnists deploy. But to the extent that Biden really is the candidate of moderate Democrats, it’s also evidence for a longtime Team Sanders argument — that Bernie has an underrated appeal to a certain kind of culturally conservative, economically liberal voter who wouldn’t normally be drawn to a candidate of the extreme left.

If that’s the case, then Sanders might have a better strategy available than the fend-off-Warren approach he’s taking at the moment. Because presumably the demographic choosing between Biden and Bernie isn’t looking for the candidate who has the most rigorously Scandinavian vision, the most fully fleshed-out theory of revolutionary change. Instead they want someone who seems to be on their side against the plutocrats, who seems to prefer economic fights to cultural ones, and who can be trusted to beat Trump and not to be a fool or fanatic once in office.

If we assume that Sanders passes the first two tests, then his mission should be to peel off Biden voters by reassuring them on the third count — telling them that he’s more than just a radical, that he isn’t allergic to compromise, that he can actually make deals and work the inside game. That it’s safe to vote for him, in other words, if you like the man but aren’t sure about the revolution.