Rand Paul leaves a press conference in Washington in March.

Breaking with many Republican colleagues, the Kentucky senator Rand Paul has revealed his concern over Donald Trump’s nomination of Brett Kavanaugh to replace Anthony Kennedy on the supreme court.

Paul told Fox and Friends on Sunday he was worried Kavanaugh, a judge on the DC circuit court of appeals, could cancel out supreme court justice Neil Gorsuch’s vote on fourth-amendment cases and allow the federal government to collect the phone records of millions of Americans.

Kavanaugh’s confirmation rests on a knife edge. Republicans hold a 51-49 advantage in the Senate. They need a simple majority or a tie broken by Vice-President Mike Pence to confirm Kavanaugh as Trump’s second supreme court pic, after Gorsuch.

With John McCain absent through illness and Democrats promising all-out opposition to a pick that could tilt the court to the conservatives for a generation, public attention has focused on three Democrats facing re-election in Republican states and two moderate GOP senators. Susan Collins of Maine and Lisa Murkowski of Alaska are considered possible opponents of Kavanaugh, based on his position on abortion rights.

Democrats may not put too much faith in Paul as an ally. In March, the Kentucky senator said he would do “whatever it takes” to block the approval of Mike Pompeo as secretary of state, over the former congressman’s views on the Iraq war and interventionist foreign policy. In April, Paul flipped and approved the nomination.

Furthermore, in 2016 Paul called Trump “a delusional narcissist and an orange-faced windbag” and said “a speck of dirt is way more qualified to…