Senate Democrats criticized the withholding of documents ahead of Tuesday’s start of confirmation hearings for President Donald Trump’s Supreme Court nominee Brett Kavanaugh, even as a top Republican predicted he would be approved by a healthy margin.

Senate Minority Leader Chuck Schumer of New York said in a tweet that the decision to hold back more than 100,000 pages of documents from Kavanaugh’s work in President George W. Bush’s administration was unprecedented for nominees and “has all the makings of a cover up.” Dick Durbin of Illinois, the No. 2 Senate Democrat, said only 6 percent of material requested will be released “if we are lucky.”

“If he’s so proud of his conservative credentials, show us the record, stand before us, trust the American people and they will trust you,” Durbin said on “Fox News Sunday.”

The Senate Judiciary Committee said Saturday that the release of records is nearly complete. But William Burck, a lawyer representing Bush in the document production, said in a letter released by the committee that after conferring with the White House and the Justice Department, some records would be withheld on the grounds of executive privilege.

According to the letter, the bulk of the documents withheld cover “deliberations and candid advice” about potential nominees for federal courts, while the remainder include substantive communications between Bush and his staff regarding executive orders and legislation. Kavanaugh “dealt with some of the most sensitive communications of any White House official,” the letter said.

An assertion of executive privilege, used to block release of information to Congress, the courts or the public on grounds of national security or to protect private White House deliberations, can only be made by a sitting president. Trump’s White House is asserting the privilege to protect communications of the Bush White House.

While Republicans have emphasized that more than 440,500 pages of material from Kavanaugh has been released, Democrats have fought for greater access to documents from his time as a lawyer in the Bush administration before being confirmed as a federal judge in 2006. Those documents, they say, would provide insights into his thinking on issues including abortion and presidential investigations.

“It’s not normal,” Democratic Sen. Amy Klobuchar of Minnesota, who like Durbin is a Judiciary Committee member, said on NBC’s “Meet the Press” about the withholding of documents. She added that documents she’s seen raise “very interesting questions” about the nominee’s views that she’s unable to discuss.

Republicans said Kavanaugh’s views can be better assessed by studying the more than 300 opinions he has written as a record as a judge on the federal appeals court in Washington.

“The Democrats have more than enough information to understand that this is a highly qualified jurist that should be the next Supreme Court justice,” Republican Sen. Ron Johnson of Wisconsin said on ABC’s “This Week” on Sunday. “In an earlier time, 30 years ago, he would have passed unanimously.”

Republicans in 2017 eliminated the 60-vote barrier to setting a vote for Supreme Court nominees, leaving Democrats without the tool of a filibuster to delay Trump’s pick.

Sen. Lindsey Graham, a Republican from South Carolina and a member of the Judiciary Committee, said on “Fox News Sunday” that he believes Kavanaugh will be confirmed and may get as many as 55 votes.

Republicans holds 50 seats in the Senate but presumably will soon get another after Arizona Gov. Doug Ducey, a Republican, nominates a successor to fill the vacancy left by the death of Sen. John McCain. Some Democrats facing re-election in November in states won overwhelmingly by Trump in 2016 are also likely to side with Republicans on Kavanaugh’s nomination.

Kavanaugh’s nomination to fill the seat held by Justice Anthony Kennedy, who stepped down at the end of the Supreme Court’s term in June, has worried some senators concerned about his views on decisions such as Roe v. Wade in 1973, which established a woman’s right to obtain an abortion.

Kennedy, viewed as a moderate and often a swing vote on the court, upheld abortion rights in a key 2016 decision that struck down a Texas law that could have forced many providers of the procedure in the state to shut down.

Graham said Kavanaugh “will give great deference, I’m sure, to Roe v. Wade. But it can be overturned like every other decision, but that will be up to the facts on the record.”

In a separate appearance on CNN’s “State of the Union,” Graham said that “precedent is important but it’s not inviolate.”

Durbin also raised concerns about Kavanaugh’s views on presidential accountability, given the convictions of Trump associates stemming from special counsel Robert Mueller’s investigation into Russian interference in the 2016 election and potential collusion by the Trump campaign.

“There is a serious question whether this president, given the opportunity, will end the Mueller investigation,” Durbin said. “We ask, of course, Judge Kavanaugh, what do you think, and he says it’s hands off when it comes to a president during his term in office.”

Asked whether Kavanaugh should recuse himself if confirmed from any cases that involve investigations of Trump, Johnson said it depends on the case but judges generally be involved.

“I’m sure Judge Kavanaugh will follow the, you know, the guidelines and recuse himself in cases where he should,” Johnson said.

Durbin said Kavanaugh was zealous while working for Independent Counsel Kenneth Starr, who led the Whitewater investigation of President Bill Clinton, but changed his mind after working in the Bush administration.

In a 2009 article for the Minnesota Law Review, Kavanaugh argued that civil and criminal investigations were “time-consuming and distracting” for a sitting president, and that congressional action was needed to defer them.