But Amash’s campaign against Kavanaugh is noteworthy for its isolation: Out of 287 elected Republicans in Congress, he appears to be the only one to vocally oppose the president’s nominee. Kennedy’s retirement and a quickly leaked list of finalists to replace him spawned a two-week debate on the right over Kavanaugh and three other contenders, Judges Amy Comey Barrett, Raymond Kethledge, and Thomas Hardiman.

Conservatives like Senator Ted Cruz of Texas and activist Erick Erickson questioned whether Kavanaugh would end up disappointing them on the high court, pulling for Barrett instead. They cited rulings in which he narrowly—rather than broadly—ruled against the Affordable Care Act and abortion rights. Once Trump announced his pick, however, the party overwhelmingly fell in line behind Kavanaugh, leaving Amash to oppose him on his own. “By any measure, Judge Kavanaugh is one of the most respected federal judges in the country,” Cruz said. “He has over 300 published opinions, with a strong record of defending the Second Amendment, safeguarding the separation of powers, reining in the unchecked power of federal agencies, and preserving our precious religious liberties.”

Party unity is especially key to this process, because unless cancer-stricken Senator John McCain of Arizona makes an unexpected return to Washington in the coming weeks, a single Republican defection would doom Kavanaugh’s nomination. Democrats have targeted Senators Susan Collins of Maine and Lisa Murkowski of Alaska because of their support for abortion rights, and while they have not vowed to support Kavanaugh, they have made positive initial comments about his qualifications.

They are not expected to oppose him on Fourth Amendment grounds, however. Amash’s challenge, then, will be to persuade either of his two main Senate allies in the privacy fight, Rand Paul of Kentucky or Mike Lee of Utah, to take up the cause. (Amash was unavailable for an interview for this story, his office said.)

Paul has already signaled his vote may be up for grabs, telling Fox News he is “concerned about Kavanaugh.” Like Amash, he compared the judge unfavorably to Justice Neil Gorsuch, the president’s pick to take the late Justice Antonin Scalia’s seat on the Supreme Court.

“I am worried, though, and somewhat disappointed that perhaps Kavanaugh will cancel out Gorsuch’s vote on the Fourth Amendment,” Paul said Sunday. The Kentucky senator cited Kavanaugh’s concurrence in a 2015 case upholding the constitutionality of the NSA’s warrantless collection of telephone metadata. “In my view,” Kavanaugh wrote, “the government’s metadata collection program is entirely consistent with the Fourth Amendment.”

He added that the “critical national security need” demonstrated by the government “outweighs the impact on privacy occasioned by the program.”