Jonathan Bernstein: “One thing that reliably gets me angry is amateurs jumping into politics at the highest level without having learned how the U.S. system works. Another is mindless Congress-bashing. Tom Steyer, an activist and former hedge-fund manager now running for president, is managing to do both.”

“House Republicans plotting to win back their majority in Congress fear they are on the brink of a massive wave of retirements that could force them to play defense in a high-stakes presidential election year,” The Hill reports.

“Three House Republicans said last week they would not seek another term next year, catching party strategists off guard. Those announcements came earlier than in a typical election cycle, when members who are ready to hang up their voting cards usually wait until after the August recess or after the Christmas break.”

A new Emerson poll finds Joe Biden leads the Democratic field with 33%, followed by Bernie Sanders at 20%, Elizabeth Warren at 14%, Kamala Harris at 11%, Pete Buttigieg at 6% and Beto O’Rourke at 4%.

Key finding: “Sanders re-established his lead among 18-29 year olds receiving 36% support among that age group.”

Rick Klein: “Two progressive powerhouses will be center stage for night one of the second Democratic debate on Tuesday. The party will be watching for Sen. Bernie Sanders and Sen. Elizabeth Warren to mix it up, knowing that they’re treading in the same ideological territory.”

“But the two New England senators are longtime allies who don’t actually disagree on very much. The real action in Detroit could come from podiums closer to the wings, where a group of relative moderates — including several who are unlikely to qualify for future debates, minus a big splash — stand ready to bring the fight.”

Politico/Morning Consult poll: “Roughly one third of voters who plan to participate in the Democratic primary or caucus in their state, 34 percent, say they are ‘very motivated’ to watch the debates on Tuesday and Wednesday. Another 39 percent indicated they were ‘somewhat motivated’ to watch. Fifteen percent said they were ‘not very motivated’ to watch, and only 8 percent said they weren’t motivated at all.”

Politico: “Democratic presidential candidates took one big lesson from their first debates in June: The contenders who shined brightest attacked other candidates onstage. Now, they are all preparing to trade punches ahead of round two in Detroit.”

“Across the Democratic presidential field, candidates are reading up on points of contrast with key rivals and preparing attack lines, while some are going a step further and simulating debate-stage cross-talk with staffers, practicing ways to butt into the conversation and create a memorable moment. Campaigns are studying how CNN handled past primary debates, when the hosts teed up opportunities for GOP candidates to criticize each other in 2015.”