The Democratic civil war is just getting started for Chuck Schumer

Chuck Schumer's headaches may only just be getting started after the Senate minority leader's handpicked candidate to take down Sen. Susan Collins was forced to drop out early in Maine's Democratic primary.

Why it matters: Progressive candidates are mounting serious, well-funded campaigns against more traditional Democrats in Senate primaries across the country.

• 🧳 Moderate Democrats are worried that progressive candidates, especially those with baggage, will hurt their chances of flipping key Senate seats if nominated.
• 🍪 Progressives argue that party leaders are relying on an outdated, cookie-cutter formula to determine who is "electable."
• 🦪 After oyster farmer Graham Platner became the Democrats' presumptive Senate nominee in Maine over Gov. Janet Mills, Senate leaders have more anti-establishment fights ahead.

Zoom in: Here's a guide to the biggest upcoming Democratic Senate primaries that exemplify the party's civil war:

1. ⛴️ Michigan: Rep. Haley Stevens is the establishment favorite and is seen by the Democratic Senatorial Campaign Committee as the strongest candidate in the fall. Polls show she's locked in a tight race with the Bernie Sanders-backed former public health official Abdul El-Sayed and the digitally savvy liberal state Sen. Mallory McMorrow.
2. 🏕️ Minnesota: Rep. Angie Craig, a battle-tested swing-seat Democrat, is viewed by liberals as the party leaders' preferred candidate. Peggy Flanagan, the progressive lieutenant governor who has attacked Craig as too squishy on ICE, has led in polling.
3. 🐷 Iowa: Schumer and his allies believe Josh Turek, a state lawmaker and Paralympic gold medalist, has the best chance in the general election. Recent polling conducted by a group supporting Turek shows him ahead by a comfortable margin. But Turek's progressive opponent, Zach Wahls, matched him in first-quarter fundraising, and past polls have shown him as more competitive.

The other side: Even though Schumer (D-N.Y.) whiffed in Maine and faces messy primaries in the near future, he also successfully recruited top Democratic candidates in Ohio, Alaska and North Carolina.

• Former Sen. Sherrod Brown, former Rep. Mary Peltola and former Gov. Roy Cooper, respectively, are widely seen in the party as star recruits.
• Schumer and Platner have spoken over the phone since Mills exited the race. Also, the DSCC has not endorsed any candidates in Michigan, Minnesota or Iowa.

The bottom line: "If you spend any time on the ground in Iowa, in Michigan, in Minnesota ... you will be absolutely floored with the intensity and the anger of Democratic primary voters," Bill Neidhardt, a Democratic strategist working to elect some of the anti-establishment Senate contenders, told Axios.

• Their fury is "not comprehended in the least by a lot of folks in D.C.," he said.
• "Our focus is on winning a Democratic Senate majority in November," said DSCC spokesperson Maeve Coyle. "We created a path to do that this cycle by recruiting formidable candidates, expanding the map and disqualifying Republican opponents — and we are confident those strategies will lead us to victory."