Jeff Roberson / AP

Claire McCaskill has two words for her progressive critics: “Shut up.”

In a Thursday interview with The New York Times, the outgoing Missouri senator described her frustration—among other grievances—that some of her fellow Democrats saw her as too quiet on the issue of abortion during the confirmation process for Supreme Court Justice Brett Kavanaugh.

“Really? This is hard,” McCaskill said of running as a Democrat in a red state. “I have been standing in the breach for women’s rights as it relates to reproductive freedom for all of my adult life, and the fact that these [critics] didn’t realize that and just be quiet, roll up their sleeves, and work their ass off for me was beyond irritating.”

McCaskill’s comments help illustrate one of the central dilemmas facing the Democratic Party: To maintain and expand its congressional majority, should the party fully embrace progressivism and all its tenets? Or should it accept the idea that the definition of “Democrat” might be slightly different in every state? Answering these questions is crucial as Democrats begin to flex their legislative muscle in the House—and as they position themselves for the 2020 elections.

McCaskill, who served 12 years in the U.S. Senate before she lost to Josh Hawley, Missouri’s Republican attorney general, in November, has a reputation as a moderate—someone who prioritizes bipartisanship, and is always positioned smack-dab in the middle of charts plotting the ideology of members of Congress.

Throughout her tenure, McCaskill has consistently voted to protect abortion access, but because Missouri has many antiabortion voters, she mostly avoids talking about it on the campaign trail. Recently, though, the issue has become particularly fraught for her.

During the recent confirmation process for President Donald Trump’s conservative Supreme Court nominee, red-state Democrats such as McCaskill and North Dakota’s Heidi Heitkamp spent weeks deliberating over how to vote. Conservatives in their states supported Kavanaugh, but progressives feared his confirmation would spell the end of Roe v. Wade and abortion access in America. “No matter how I vote, there’s going to be a lot of people who are not going to be happy with it,” McCaskill said at the time. The Missouri Democrat ultimately voted against Kavanaugh, but not because of abortion or the sexual-assault allegations against him. Instead, McCaskill said she voted no because of an email Kavanaugh had written to a colleague in 2002, which seemed to suggest that he thought there were “constitutional problems” with limiting campaign contributions to candidates.

“There are some voters that the only issue they care about is outlawing all abortions, and there are other voters that the only issue they care about is keeping access to abortion legal,” McCaskill told reporters ahead of the Senate vote. “What is more common is a large number of people concerned about ‘dark money.’”

In June, as part of an effort to erase some of the gains Republicans had made in the 2016 election, the Missouri Democratic Party had altered its platform to welcome Democrats who oppose abortion. McCaskill, for her part, praised the move. But almost immediately, progressives and abortion-rights activists both inside and outside the state began to protest. By August, Missouri Democrats had removed the provision.

McCaskill’s openness to antiabortion Democrats has earned her criticism from those in her party who argue that all its members should be unapologetically pro-choice. But the senator says she worries that without empowering moderates, Democrats will never regain a majority in both chambers of Congress. “This demand for purity, this looking down your nose at people who want to compromise, is a recipe for disaster for the Democrats,” she told NPR in November. “Will we ever get to a majority in the Senate again, much less to 60, if we do not have some moderates in our party?”

Others go even further—and say that the party should support only full-throated progressives to be successful. Shortly after winning their elections in November, incoming Representatives Alexandria Ocasio-Cortez of New York and Rashida Tlaib of Michigan announced that they would work with Justice Democrats, a progressive political-action committee, to recruit working-class candidates to challenge more conservative Democrats in the House.

The move—which some Democrats have characterized as a progressive purity test—could foreshadow problems in the next Congress and in future elections, with passionate progressives attempting to steer the direction of the party. And to some Democrats, it appears to disregard the lessons of the midterms: Nearly all the candidates who flipped seats from red to blue are political moderates. These Democrats believe their party won a House majority in November not because of outspoken progressives like Ocasio-Cortez, who defeated the prominent Democrat Joe Crowley in a primary in June, but because of pragmatist Democrats who ran in red districts and emerged victorious. People a lot like Claire McCaskill.

“God love her,” McCaskill said of Ocasio-Cortez on Thursday, “but I hope she listens to the people who defeated Republicans, because it’s the people who defeated Republicans in this election that we need to be emulating.”

Progressives, she said, “need to remember who their friends are and not make it more difficult for their friends.”

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