WASHINGTON (TNS) — 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.

Senate Minority Leader Charles E. Schumer, D-N.Y., said on Twitter 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." Richard 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, most 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.

While Republicans have emphasized that more than 440,500 pages of material from Kavanaugh have been released, Democrats have fought for more 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," Sen. Amy Klobuchar, D-Minn. — who, like Durbin, is a Judiciary Committee member, said on NBC's "Meet the Press" about the withholding of documents. She said the 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," Sen. Ron Johnson, R-Wis., said on ABC's "This Week." "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, R-S.C., 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 hold 50 seats in the Senate but presumably will soon get another after Arizona Gov. Doug Ducey, a Republican, appoints 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.