If you want to make a politician really, really angry, endorse their primary opponent. That's exactly what Bernie Sanders did Saturday to Democratic National Committee Chairwoman Debbie Wasserman Schultz.
"Clearly, I favor her opponent," Sanders said in an interview with CNN's Jake Tapper. "His views are much closer to mine than as to Wasserman Schultz's. Let me also say this, in all due respect to the current chairperson: If (I am) elected president, she would not be reappointed chairwoman of the DNC."
That puts Sanders on the side of Tim Canova, a former Capitol Hill staffer who has enjoyed considerable fundraising success -- he's raised more than $1 million -- thanks to an anti-establishment message in his primary against Wasserman Schultz.
And it ensures that the nastiness between Sanders and his supporters and Wasserman Schultz and the mainstream Democrats she represents will now surge into a full-blown battle.
Here's why: Wasserman Schultz is a professional politician. Serving as DNC chair, she's been on the receiving end of plenty of attacks -- both from Republicans and even Democrats -- over the last few years. It might annoy her, but she's learned to live with it.
What Sanders is doing is something different. He's not only questioning her ability to oversee the party. He's going after her livelihood -- her day job. And that's deeply personal.
I have talked to former pols -- and even ones still in office -- who still hold grudges against colleagues who endorsed against them in a tough primary fight. They never forget. And, almost to a person, they never forgive.
You can be certain that Wasserman Schultz has spent the past 12 hours making sure that every one of her colleagues is aware of what Sanders has done. If he is willing to do this to me, don't fool yourself into thinking he won't do it to you too, she'll argue. Yes, that's a fundraising ploy. But, it also speaks to the very real threat that a free radical like Sanders presents to the established order.
That's exactly how Sanders likes it. His brand is shaking up the establishment -- just as he has done in the presidential race against Hillary Clinton. His supporters will love that he is willing to put some political capital on the line against Wasserman Schultz, who many of them believe is rigging the race for Clinton behind the scenes.
What Sanders has done with this endorsement is to amp up the tension on both sides of the fight. And, tensions were already pretty high.
Remember that this past week featured a major confrontation between Clinton and Sanders supporters at the Nevada Democratic convention and a war of words between Sanders and Wasserman Schultz over the appropriate level of condemnation necessary for the events in Nevada.
Clinton, too, has spoken out in more-aggressive-than-usual terms about Sanders and why he needs to begin planning how he wants to leave the race.
Now that Sanders has endorsed Wasserman Schultz's opponent, everything is even more personal than it was 24 hours ago. And when things get personal, reason and pragmatism often fly out the window.
That's bad news for Democrats hoping to quickly unite the party in advance of the general election fight against Donald Trump.
It's war now.