Republican senators who strongly opposed the government’s collection of domestic call records say they still are reviewing the record of Supreme Court nominee Brett Kavanaugh, who authored a broad defense of the program.

Many senators viewed the National Security Agency's call record dragnet as a violation of the Fourth Amendment, and Congress voted to end the once-secret collection months before Kavanaugh authored a 2015 concurrent opinion finding it legal.

Kavanaugh wrote the collection wasn't a “search” under the Fourth Amendment, citing the third-party doctrine of the Supreme Court's 1979 decision in Smith v. Maryland. But he added if it was a “search," authorities still could take the records without a warrant because there was a “special need” in preventing terrorism, overriding privacy interests.

Although the program stored call records for five years for potential later use in intelligence investigations, a 2014 report from the Privacy and Civil Liberties Oversight Board said there was no evidence it ever led to the detection of a terrorist plot.

Republicans hold just 51 seats in the Senate, and with the ill Sen. John McCain, R-Ariz., not expected to vote, even one GOP defection could threaten Kavanaugh, particularly if Democrats unite in opposition. But so far, libertarian-leaning privacy members have withheld judgment.

Opposition to NSA mass surveillance programs is bipartisan, with libertarian and progressive lawmakers generally struggling to restrain the authorities against centrist backers of broad collection powers. In the Senate, Sens. Rand Paul, R-Ky., and Mike Lee, R-Utah, led opponents of collection programs exposed in 2013 by whistleblower Edward Snowden.

Paul unilaterally forced provisions of the USA Patriot Act to lapse in 2015 to demonstrate his opposition to the call record dragnet — dismissing executive branch claims that doing so would harm national security. But Paul hasn’t spoken publicly about Kavanaugh's support for what Paul called an “illegal program.”

“If there ever was a general warrant … this is it,” Paul said in a 2015 speech before forcing the 2001 anti-terror law to partially lapse.

[Related: The Left's dismally weak case against Brett Kavanaugh]

“We are not collecting the information of spies; we are not collecting the information of terrorists," Paul said. "We are collecting all American citizens’ records all of the time. This is what we fought the American Revolution over. Are we going to so blithely give up our freedom? Are we going to so blithely go along and just say ‘take it’? Well, I’m not going to take it anymore.”

After President Trump nominated Kavanaugh, Paul issued a noncommittal tweet, a contrast from his initial vow to block secretary of state nominee Mike Pompeo and CIA director nominee Gina Haspel earlier this year. Both ultimately were confirmed, with Paul voting for Pompeo after he agreed to call the Iraq War a mistake and say it was time to leave Afghanistan.

Paul tweeted Monday: “I look forward to the upcoming hearings, reviewing the record, and meeting personally with Judge Kavanaugh, with an open mind.”

Throughout the week, Paul spokesman Sergio Gor said he could not comment beyond the tweet.

Sen. Mike Lee, R-Utah, a libertarian-leaning Republican who helped author the USA Freedom Act that ended the call-record program, was similarly restrained.

“Sen. Lee has been a consistent advocate for Fourth Amendment rights. He looks forward to closely analyzing Judge Kavanaugh’s record on the issue during the upcoming confirmation process,” Lee spokeswoman Jillian Wheeler told the Washington Examiner.

“Sen. Lee is still analyzing Kavanaugh’s records, including on the Fourth Amendment,” Wheeler said.

But in tweets immediately after his selection, Lee — who Trump interviewed as a Supreme Court candidate — indicated he viewed Kavanaugh favorably.

“Judge Kavanaugh is a well-respected jurist who deservedly received bipartisan support when confirmed to the D.C. Circuit in 2006. I know him to be a smart and fair judge, one of the most admired appellate judges in the country,” Lee tweeted Monday.

In a second tweet, Lee wrote, “I look forward to the process in the Senate, getting to know Judge Kavanaugh and his family better in coming months, and, hopefully, voting to confirm him to the Supreme Court in the fall.”

Although only the Senate will vote on the nomination, House Republicans hostile to the NSA dragnet also have been restrained, with the notable exception of Rep. Justin Amash, R-Mich., who organized a narrowly defeated House amendment to end the program in 2013.

“Trump nominates judge who supported Obama NSA spying. Rs in Congress: Yay!” Amash tweeted Tuesday.

“Kavanaugh is not another Gorsuch — not even close," Amash wrote. "Disappointing pick, particularly with respect to his #4thAmendment record. Future decisions on the constitutionality of government surveillance of Americans will be huge. We can’t afford a rubber stamp for the executive branch.”

Before he was nominated, another prominent conservative, Senate Conservatives Fund President Ken Cuccinelli, told the Washington Examiner he believed Kavanaugh was an “excellent judge” but that “his Fourth Amendment perspective is troubling."

Cuccinelli, a former Virginia attorney general, represented Paul in a lawsuit challenging the constitutionality of the call-record program. Paul’s case was hitched to conservative legal activist Larry Klayman’s lawsuit in the same circuit. Klayman’s case was the one denied by Kavanaugh.

“As someone who sued the NSA over their metadata gathering as a violation of the Fourth Amendment, he and I disagree on that point, and I think a lot of liberty-minded folks are going to have that as a major concern,” Cuccinelli said about Kavanaugh before his nomination.

Whether Fourth Amendment concerns alone are enough to peel off senators remains to be seen. Republicans will be heavily pressured to support Kavanaugh, as a failed nomination would be a major political defeat and personal embarrassment to Trump.

Although senators like Lee and Paul are passionate about Fourth Amendment issues, it’s possible they will find Kavanaugh acceptable by looking more expansively at his record.

Rep. Thomas Massie, R-Ky., who has sponsored legislation to force the NSA to get a warrant to search “incidentally” intercepted domestic records, offered a more comprehensive assessment of Kavanaugh this week.

“I think he’s going to be with us on guns,” Massie told Cincinnati radio host Brian Thomas on Wednesday, saying later, however, that “he is weak on the Fourth Amendment. He is flat-out bad on the Fourth Amendment; let’s be honest.”

“For people who are upset with his position on the Fourth Amendment, what they are upset about is he didn't strike down laws that Congress put in place,” Massie added. (There is significant debate about whether the USA Patriot Act actually authorized the call record dragnet. Many members of Congress did not know about its existence, and a New York federal appeals court panel found in 2015 the collection exceeded the law’s mandate.)

Some Republicans hostile to the call dragnet appear less inclined to question Kavanaugh’s stance on the issue. He was almost immediately endorsed as an "excellent choice" and a "strong willed constitutionalist" by Rep. Ted Poe, R-Texas, co-chairman of the bipartisan Fourth Amendment Caucus.

In response to a question specifically about the Fourth Amendment, the office of Sen. Dean Heller, R-Nev. — one of the few Republicans routinely siding with Paul and Lee on surveillance issue — sent a statement that hailed the judge as having "a record of adherence to the Constitution."

Other issues have received greater press attention in the days since President Trump nominated Kavanaugh, such as speculation about what his confirmation might mean for the future of abortion access. There's also been signficant attention on his personal finances, including recent credit card debt that the White House says is related to purchasing baseball tickets.

Snowden, the former NSA contractor who exposed the call record program, declined to comment on Kavanaugh’s nomination.

ACLU National Political Director Faiz Shakir, however, suggested there’s room for a fight.

"Given this record, it’s essential that Kavanaugh be questioned extensively and directly about his commitment to protecting Americans from unlawful searches and seizures, and we’re glad to see Senators Rand Paul and Ron Wyden are among the few who are willing to investigate these positions,” Shakir said. “The public also deserves to see all documents from Kavanaugh’s time at the [George W. Bush] White House demonstrating what he knew about the surveillance programs and what role he may have played in their development."