Senate Democrats scrapped again Thursday with Sen. Charles E. Grassley (R-Iowa) in their latest attempt to pressure the Judiciary Committee chairman into backing off a pledge to block President Obama’s forthcoming Supreme Court nomination, while the leader of the Congressional Black Caucus said a blockade would “energize” voters in an unprecedented way.

At one point, Grassley took the unusual step of moving from the Senate floor, where he was managing pending legislation, to the presiding officer’s seat in an apparent bid to end an extended Democratic attack on his decision to cancel a previously scheduled committee meeting.

Sen. Patrick J. Leahy (D-Vt.), the committee’s top Democrat, took aim at Grassley for convening the panel’s Republicans behind closed doors in Senate Majority Leader Mitch McConnell’s (R-Ky.) office last week — a meeting resulting in a pledge to deny any Obama high-court nominee a hearing.

The full committee has not met since to discuss the nomination or any other topic. A Thursday morning meeting was canceled, Grassley said, after Democrats rejected his “routine” request to move it to a private room off the Senate floor — where TV cameras would have been prohibited — to accommodate his need to manage the narcotics bill now on the Senate floor.

“The American people deserve to hear us discuss and debate the Committee’s next steps in fulfilling our constitutional duty,” Leahy said.

Grassley, whom Democrats have targeted in their efforts to force consideration of a nominee, dismissed the attacks as “unfortunate political gamesmanship” and accused Democrats of using the Supreme Court dispute to hold up the narcotics bill. “The opioid epidemic is not a political game,” he said. “It’s a real problem out there.”

“The other side knows that the nominee is not going to be confirmed,” Grassley said in a subsequent floor speech. “Everyone knows it. The only reason that they’re complaining … is because they want to make the process as political as possible. We’re not getting to politicize this process in the middle of a presidential election year. We’re going to let the people have a voice.”

While Democrats hammer away at Grassley, Senate Republican leaders are maintaining faith in his ability to withstand the pressure, believing that he is absolutely unwilling to cross his base of conservative voters on what they consider a deeply crucial issue.

At a Wednesday afternoon meeting of dozens of conservative activists in McConnell’s office, including the National Rifle Association, the National Right to Life Committee, and other groups invested in the court fight, Grassley gave a stout defense of the blockade, according to a person who was present, winning a loud ovation from the audience.

But at a news conference where Senate Democrats were joined by members of the Congressional Black Caucus, lawmakers pointed to a new CNN poll that found two-thirds of Americans believe that Obama’s nominee should get a Senate hearing. But about half say Republicans would be justified in blocking a final vote on that nominee.

Rep. G.K. Butterworth (D-N.C.), the CBC’s chairman, said he had been approached by even Republican constituents “disappointed” by the blockade. “This issue is going to be viewed by the American people for what it is: It’s obstruction at its worst, and, yes, I believe it will energize many people — Democrat, Republican and independent — to participate in this election unlike any in our nation’s history,” he said.

Democrats continue to view Grassley, a six-term Senate veteran who is up for reelection this year, as a prime target in their efforts to break the blockade, believing that appeals to his sense of legacy and fair play will ultimately force him to relent.

In another development that could increase pressure on Grassley, a Democratic former lieutenant governor in Iowa, Patty Judge, is expected to launch a campaign challenging his bid for a seventh term.

A person familiar with Judge’s plans but not authorized to comment publicly ahead of a formal announcement confirmed a likely Friday launch. Democratic campaign strategists have not previously targeted the chairman, believing that Grassley had a firm hold on the seat he has held since 1981.

But the politics of the Supreme Court nomination battle have somewhat changed that calculation. Judge, 72, is not expected to earn an immediate commitment of resources from national Democratic campaign organs, but her record of holding statewide office is thought to make her a more compelling candidate than the current and former state lawmakers who have already entered the race.

The Iowa Democrat most sought by national campaign recruiters, former governor and current Agriculture Secretary Tom Vilsack, has shown no interest in a Senate run.

In an interview with The Des Moines Register last week, Judge confirmed she was considering a run and suggested it was Grassley’s Supreme Court stance that convinced her to do so.

“Iowans have always been straight shooters, and up until the recent time I would have said the same thing about Chuck,” she told the paper, adding, “I think Chuck Grassley owes us better. He’s been with us a long time. Maybe he’s been with us too long.”

Judge could not be reached Thursday. The New York Times first reported news of her run. To qualify for the primary ballot, she has until March 18 to collect signatures across the state.