Until late this afternoon, the central mystery about tonight’s Democratic debate was just how much of a beating the new frontrunner in Iowa — and New Hampshire? — will end up taking from his colleagues. This will be an all-out pile-on, make no mistake. Pete Buttigieg is a cool customer, very sharp, a skillful debater based on the evidence so far, but the sheer number of criticisms he’s apt to face should put a dent in his numbers. How much of a dent?

As I say, that was the source of this evening’s suspense. But in light of late-breaking news, there’s a new source:

Will anyone congratulate Joe Biden on his new grandchild? Hoo boy.

Back to the substance. What makes this a fun debate is the fact that virtually the entire remaining Democratic field resents Buttigieg ferociously, either for “stealing” votes that more properly belong to them or for putting them on the defensive about their policy plans. Who is this thirtysomething interloper who’s never held federal or statewide office, suddenly leading the pack in the early states? How dare he cynically reposition himself towards the center when he began the race as a more or less dogmatic progressive?

Every member of the top tier and various members of the lower tiers have the means and motive to clobber him tonight. Biden’s going to smack him for his lack of experience (“I was in the Senate when you were in diapers, son”), knowing how Buttigieg could cannibalize some of his centrist support. Warren and Sanders are going to wreck him for conveniently deciding to turn against Medicare for All at the moment space seemed to open up in the centrist lane. Cory Booker and Kamala Harris will litigate Buttigieg’s record on race relations, hoping to knock him down in Iowa and gain some traction in South Carolina. Tulsi Gabbard may come at him for his more hawkish foreign policy views.

And Amy Klobuchar — well, given how much she seems to dislike Buttigieg, there’s no telling how ugly it might get:

Over the summer, a simple mention of Mr. Buttigieg’s name during a conversation in the Senate chamber between Senator Cory Booker of New Jersey and Ms. Klobuchar was enough to make Ms. Klobuchar extremely agitated, according to witnesses.

Ms. Klobuchar, during an interview last weekend in Iowa, declined to answer when asked if Mr. Buttigieg is qualified to be president. Instead she pointed to his electoral record, which she said shows no signs he could beat President Trump in a general election.

“I think it’s important to look at someone’s track record to see what’s happened when they’ve run statewide,” she said. “There’s got to be some value put on someone that has been able consistently to show that they can bring people with them. Not in one fluke race, but every single time.”

You know what happens when Amy Klobuchar gets angry? Staffers die, that’s what happens.

Klobuchar’s going to hit him the hardest, I’d guess, as Buttigieg seems to be occupying what she hoped would be her niche in the top tier. She’s running as a low-key midwesterner who straddles the left and the center, perfectly positioned to pick up disaffected Joe Biden voters as they give up on him but also well placed to draw lefties who want a leftist president but aren’t completely comfortable with the sort of socialism in full flower that Bernie and, to a lesser extent, Elizabeth Warren are offering. And that strategy is working like a charm — for Pete Buttigieg, who’s filled that space instead of Klobuchar. He’s the mayor of a small city, she’s a thrice-elected U.S. senator who’s won by landslide margins every time. And to this point he’s elbowed her aside so effectively that she’s been reduced to huffing that a woman with Buttigieg’s degree of inexperience would never be taken seriously as a presidential candidate.

She’s gonna throw that at him tonight. And it’ll be funny when he very calmly agrees and burbles something soft and thoughtful about “male privilege” that completely gets him off the hook. Lefty voters seem to be cheap dates in the sense that they’re okay with their politicians enjoying privilege so long as they acknowledge that they have that privilege, combined with some empty rhetoric about doing more to ensure that everyone enjoys the same opportunities. You don’t actually need to do anything about creating opportunities. Signaling that you care is enough.

I’m rooting for him tonight and you should be too. Not just because he’d probably be the easiest candidate among the top tier for Trump to beat next year, but because online progressives have taken a deep dislike to him and seeing him succeed will drive them nuts. They resent him foremost for the same reason they resent all of the non-Sanders candidates in the field — he’s in Bernie’s way — but they also seem to find his appeal shallow, owing mostly to the fact that he comes off as “the straightest-A straight-A student who ever lived,” as a Twitter pal put it a few days ago. He’s Obama with less charisma (and many many many fewer black supporters), the sharp young intellectual whose commitment to radical left-wing change is hazy but who can certainly put a sentence together during an interview. HuffPost noted yesterday that Buttigieg’s smarty-pants persona has earned him waaaaaaaay more mentions in the press of his Rhodes scholarship than Cory Booker has received even though Booker has that credential too. If you’re a left-wing ideologue who believes socialism’s moment has arrived, it must be painful to see its chances threatened by a guy whose main credential seems to be that he speaks eight languages.

This utterly painful clip of Mayor Pete supporters at a rally in New Hampshire circulated widely on political Twitter a few days ago, drawing scorn from both sides. For righties it’s a straightforward “can you believe these dorks?” thing. For lefties it’s more bitter, a “can you believe these dorks would rather than dance than pass Medicare for All?” thing.

Ever seen the old SNL clip mocking the presidential debates during the 1988 campaign, when Dana Carvey as Bush 41 gives some inane rambling answer and Jon Lovitz as Dukakis responds, “I can’t believe I’m losing to this guy”? That’s every Berniebro and DSA member in the country watching that clip of Buttigieg fans do the hand-jive.

The debate airs live at 9 p.m. ET on MSNBC and its website. In lieu of an exit question, read Philip Klein on why Klobuchar might be poised to make a move in Iowa. He makes a good case — Iowa tends to break late and, as noted, Klobuchar is well positioned to soar as a compromise candidate if Dem voters decide Biden’s too meh, Bernie and Warren are too radical, and Buttigieg is too green. A lot is riding on tonight. If Klobuchar wins the battle with Mayor Pete, she may start to climb immediately. If Buttigieg wins it, that may finish her off as a pretender who just can’t compete with the top tier.