Senate Republicans are in a double bind when it comes to defending Brett Kavanaugh. Backed by President Trump and conservative activists, they’ve dug in, signaling their plan to go forward with a confirmation vote if Christine Blasey Ford, who accused Kavanaugh of sexually assaulting her at a party they attended as teenagers, chooses not to testify at the Senate Judiciary Committee on Monday. Ford wants the FBI to investigate the incident, which might not confirm her exact account but could fatally threaten Kavanaugh’s denials.

Their commitment is rational. Republicans are achingly close to cementing a conservative majority on the Supreme Court for the next generation, which will almost certainly deliver an effective end to Roe v. Wade and other legal bugaboos of the conservative movement.

But there are also short-term stakes. Presidents and parties can lose battles for the Supreme Court and still recover, but the pain will linger. A Kavanaugh collapse would worsen an already-perilous midterm environment for the GOP, demoralizing Republican voters just weeks before voting. But a Kavanaugh confirmation could prove dangerous as well. In a political moment shaped by women’s anger, from the Women’s March to the #MeToo movement, putting Kavanaugh on the court despite a credible allegation of sexual assault could prove disastrous for Donald Trump and the Republican majority in Congress.

Justice Kavanaugh might be a partisan accomplishment so toxic that it backfires on Republican politicians.

Brett Kavanaugh wasn’t the only name on Trump’s short list for the Supreme Court. The president had options. There was Amy Coney Barrett, a former law professor confirmed to the 7th U.S Circuit Court of Appeals last year with bipartisan support—and likely firm vote against Roe. There was Thomas Hardiman, a runner-up for the seat held by Neil Gorsuch and judge on the 3rd U.S Circuit Court of Appeals. There was Joan Larsen, a 6th Circuit judge and former clerk for Antonin Scalia with sterling conservative credentials. And there was Amul Thapar, also on the 6th Circuit, with strong backing from Senate Majority Leader Mitch McConnell.*

Options for Trump are also options for Senate Republicans, who could reject Kavanaugh and still confirm a replacement before the end of the year. But the political risks of rejecting the president’s favored nominee now are too high. Conservative evangelicals backed Trump in hopes of winning an anti-abortion majority on the Supreme Court. They are his most reliable constituency, one reason his job approval hasn’t collapsed entirely, and key factor if Republicans plan to survive a “blue wave” in the fall. They want Kavanaugh, and if Republicans fail to put him on the court, their support may waver.

“One of the political costs of failing to confirm Brett Kavanaugh is likely the loss of the United States Senate,” said evangelical leader Ralph Reed to the New York Times. Reed and his peers have urged the White House to push forward and ignore the allegations against Kavanaugh, under threat of political disaster. “If Republicans were to fail to defend and confirm such an obviously and eminently qualified and decent nominee,” Reed said, “then it will be very difficult to motivate and energize faith-based and conservative voters in November.”

Confirming Kavanaugh might preserve Republican turnout, but it could also energize Democrats.

Even before Ford levied her accusation of sexual assault, Brett Kavanaugh was one of the most unpopular Supreme Court nominees in recent memory. In July, according to Fox News, 38 percent of Americans said they would vote to confirm him for the court, versus 32 percent who said “No” and 30 percent who were unsure. In August, after a month of debate, 45 percent of Americans said they would vote to confirm versus 46 percent who said they wouldn’t—just 9 percent were unsure. His numbers were similarly low at the start of September: 38 percent support, 39 percent opposed, and 23 percent undecided, according to CNN.

Much of this reflects attitudes toward President Trump, whose popularity sank in the last weeks of summer, dropping from a rough average of 42 percent job approval to a rough average of 40 percent approval, a significant decline in an era of high partisanship and rigid polarization. Still, Kavanaugh’s numbers make him the least popular Supreme Court nominee since Robert Bork, rejected in 1987 by a bipartisan group of senators for his right-wing views on civil rights as well as his role in the Watergate “Saturday Night Massacre.”

Ford’s accusations have worsened Kavanaugh’s standing. Reuters/Ipsos shows a 6 point increase in opposition since its last poll in August. A Gallup poll also shows rising skepticism of Kavanaugh’s nomination. A recent NBC News/Wall Street Journal survey has Kavanaugh “below water” with voters—a first in that poll’s history.

To confirm Kavanaugh in the face of deep unpopularity and serious controversy is to make a Democratic House—and a Democratic Senate—more likely. Like the tax cuts—which were similarly unpopular—Justice Kavanaugh might be a partisan accomplishment so toxic that it backfires on Republican politicians, especially with college-educated suburban women, who are already leaving the GOP in droves. The only other option is to drop Kavanaugh for another nominee—and risk a deadly blow to conservative enthusiasm in November.

Correction, Sept. 20, 2018: This article originally misidentified Amul Thapar as being a district court judge. He was elevated to the 6th U.S. Circuit Court of Appeals in 2017.