– An intensifying debate over Judge Brett Kavanaugh, a front-runner in President Donald Trump’s search for a Supreme Court nominee, gripped Republicans Tuesday, with conservative critics highlighting past rulings and his links to GOP leaders while his allies — including inside the White House — forcefully defended him.

The sparring over Kavanaugh, one of four federal appeals court judges who met with the president Monday, underscored the challenges facing Trump as he races to pick a successor to retiring Justice Anthony Kennedy by his own July 9 deadline. Even as Trump mulls a shortlist that has been carefully cultivated by influential Republican lawyers, frictions in the conservative legal community and on Capitol Hill threaten to disrupt the search process.

The political moment for Trump remained fragile as a president devoted to his base weighed what a Kavanaugh selection could mean for him, unfolding amid a flurry of op-eds and phone calls praising the 53-year-old judge as well as a clamor from those who see him as out of step on health care and abortion, or too tied to George W. Bush’s White House.

“You hear the rumbling because if you’ve been part of the establishment for a long time, you’re suspect,” veteran conservative organizer Richard Viguerie said in an interview. “Kavanaugh carries that baggage.”

“Movement conservatives fume at Trump SCOTUS favorite,” blared a headline Tuesday in the Daily Caller, a conservative website, atop an article featuring right-wing activists with sharp words for Kavanaugh.

Trump advisers said Tuesday that the president was aware of the squabbling and closely monitoring news coverage of his interviews, but they cautioned that he has not been swayed by a particular voice.

Trump has also spoken by phone with Sen. Rand Paul, R-Ky., this week, according to three people briefed on the call who were not authorized to discuss it publicly. Paul and his advisers had quietly conveyed their concerns about Kavanaugh to the White House in recent days, citing his decisions on health care. Since Republicans hold a narrow 51-seat majority in the Senate, losing just one GOP vote could jeopardize a nominee.

“This is the whisper campaign that’s out there trying to destroy Kavanaugh and it could be legit,” syndicated radio-show host Rush Limbaugh told his listeners Monday. “The long knives are out from people from all sides of the aisle, folks.”

Kavanaugh, 53, has a long history in Washington, having helped investigate President Bill Clinton as part of independent counsel Kenneth Starr’s team and then serving as a close aide to Bush before joining the U.S. Court of Appeals for the District of Columbia Circuit in 2006.

The rush of scrutiny and objections have vexed Kavanaugh supporters, who days ago viewed him as one of the strongest prospects due to his past tenure as a Kennedy clerk and deep support among veteran Republican attorneys — and given a sudden jolt of hope to supporters of other contenders for the bench.

The questions have come from some social conservatives, a group Trump has relied on for continued and fervent support after promising during the 2016 campaign to appoint justices who would overturn Roe v. Wade, the landmark 1973 ruling that legalized abortion nationwide.

Kavanaugh’s critics have pointed to a recent case involving a pregnant immigrant teenager in federal custody as reason to doubt his conservatism on the abortion front.

He voted against the teenager, who was seeking immediate access to abortion services, and noted the government’s “permissible interest” in “favoring fetal life,” but he did not go as far as another District Circuit judge, Karen Henderson, who said the undocumented teen had no constitutional right to an elective abortion.

A 2016 case over the contraceptive mandate in President Barack Obama’s health care law has also drawn attention. Kavanaugh sided with the group Priests for Life, but in his opinion he wrote that Supreme Court precedent “strongly suggests that the Government has a compelling interest in facilitating access to contraception,” but that there were less “restrictive means of furthering” that interest.

Separately, in a 2011 challenge to Obama’s health care law, Kavanaugh dissented from a District Circuit decision upholding Obamacare, but he did so for technical and jurisdictional reasons instead of declaring the law unconstitutional, as ideological purists would have preferred.

White House counsel Donald McGahn, who is coordinating the candidate interviews for Trump, has been unpersuaded by Kavanaugh’s opponents and has spoken repeatedly and reassuringly about his credentials with top Republicans, according to three people briefed on those discussions.

The White House communications team, which set up a political war room Monday to bolster the eventual nominee, has been mum about Kavanaugh since the president has yet to make a decision, leaving the debate to play out largely without White House involvement.