The 1 thing everyone's talking about before the debate

Polling shows a four-person top tier among Iowa voters, with Bernie Sanders in the lead followed closely by Joe Biden, Elizabeth Warren and Pete Buttigieg. Further behind are Tom Steyer and Amy Klobuchar.

There may be six people on stage tonight, but just two names are driving the conversation here in Iowa: Sanders and Warren. That's because their infamous non-aggression pact broke wide open this weekend. First, reports emerged that Sanders volunteers were given a script to trash Warren.

Then, CNN reported that Sanders told Warren in a 2018 meeting that he didn't believe a woman could win the presidency. To add insult to injury, Warren publicly confirmed the story, releasing her account of the event.

Tuesday night's debate will be the first time Warren and Sanders are face-to-face since the ceasefire ended, and the first real test of just how hard the two candidates will go after each other, if at all.

Warren is indicating she's not interested in slugging it out. On Monday, she confirmed CNN's reporting, but also added that she has "no interest in discussing this private meeting any further because Bernie and I have far more in common than on our differences on punditry."

If Sanders doesn't feel heat from Warren over the comment, it could come from the other woman on stage: Klobuchar.

Klobuchar has a LOT riding on the debate and a strong performance in Iowa. She has yet to break into that top tier of candidates and has a reputation for delivering strong debate performances, kneecapping people like Buttigieg and Warren in previous debates.

This debate is Klobuchar's last chance to make a splash with Iowa voters writ large, and all signs indicate she'll jump right in.

The Point: Don't expect midwestern niceties on the debate stage in Des Moines tonight.