– Supreme Court nominee Brett Kavanaugh’s road to confirmation may have a little-noticed obstacle: Sen. Rand Paul’s firm views on privacy.

While abortion has gotten most of the attention in the partisan fight over the nomination, the Kentucky Republican strongly disagrees with Kavanaugh on the meaning of the Constitution’s Fourth Amendment, and he’s shown little reluctance to defy Senate GOP leaders or the White House to make a point on civil liberties and other privacy issues.

In a Senate controlled by the GOP 50-49 with Republican Sen. John McCain absent while fighting brain cancer, Paul’s vote can’t be taken for granted.

Paul, who ran for president with a libertarian-minded platform, so far hasn’t tipped his hand, tweeting that he’s keeping an “open mind.”

“I’m not going to make any comment until we’ve had a chance to look through and really go through a discovery process, meet the nominee,” Paul said in an interview when asked about Kavanaugh shortly before President Donald Trump announced his choice July 9.

But Paul did say he would dig into privacy issues.

He praised Trump’s first high court nominee, Neil Gorsuch, and lauded the justice’s dissenting opinion in a June 22 ruling that police generally need a warrant to get someone’s mobile-phone tower records. Gorsuch said the defendant should have pursued the appeal as a matter of property rights.

“He’s exactly where I am, and I’m just hoping we can find somebody else who’s in that same position, that you don’t give up your privacy by having a cellphone, or having a bank account,” Paul said. “Doesn’t mean the government gets to look at all that stuff without a warrant. We’re going to definitely look at all of that.”

Some of Paul’s allies are targeting Kavanaugh because of his past rulings backing the massive buildup in intelligence-gathering on Americans after the Sept. 11 attacks.

Paul himself filed a federal class-action lawsuit in 2014 claiming that the government’s collection of phone records on hundreds of millions of Americans violated the Fourth Amendment’s protection against unreasonable searches and seizures, and requiring warrants based on probable cause.

A year later, Kavanaugh wrote an opinion with the opposite view in a separate case challenging the program. “The government’s metadata collection program is entirely consistent with the Fourth Amendment,” Kavanaugh wrote. He said he was bound by a 1979 Supreme Court precedent, Smith vs. Maryland, on phone records, which Paul’s lawsuit argued should not apply.

The judge said the collection program didn’t amount to a search under the Fourth Amendment, and that even if it was a search, the impact on privacy was justified to prevent terrorist attacks.

Paul has passionately opposed such sweeping, warrantless data collection programs, filibustering their extensions on the Senate floor and championing the issue during his presidential campaign — even selling an “NSA spy cam blocker” sticker on his website to cover up the cameras on laptops.

One of the first members of Congress to endorse Paul’s presidential bid, Rep. Justin Amash of Michigan, ripped Kavanaugh last week in a series of tweets citing Kavanaugh’s metadata opinion.

“We can’t afford a rubber stamp for the executive branch,” wrote Amash, who shares Paul’s libertarian leanings. Congress has curtailed the practices at issue, ultimately rendering the legal cases moot.

If Paul were to oppose Kavanaugh based on objections to his stance on Fourth Amendment issues, it would dramatically narrow the judge’s path to confirmation. Trump would either need to find at least one Democratic vote for his pick, or coax the ailing McCain to travel to Washington and vote, or resign and be replaced by a Republican who would vote for Kavanaugh.

The independent-minded Paul briefly forced a government shutdown last year because of concerns about spending, and previously forced a lapse in surveillance authorities.

Earlier this year he led an unsuccessful effort to block Gina Haspel’s nomination to lead the CIA over concerns about torture. But actually blocking a Trump Supreme Court justice would be an altogether new level of rebellion for Paul, and he would surely face enormous pressure to relent.