Senate Majority Leader Mitch McConnell, R-Ky., could seek to hold the Senate in session longer each week to keep vulnerable incumbent Democrats off the campaign trail.

McConnell this month began threatening Senate Democrats with longer workweeks if they continue to slow-walk the confirmation of President Trump’s nominees. Marc Short, White House point man for legislative affairs, told a small gathering of Republican donors this week that the majority leader plans to use this tactic in the weeks ahead to squeeze Democrats running for re-election in red states.

“McConnell wants to increase the days the Senate is open for business to keep” Democratic Sens. Heidi Heitkamp of North Dakota, Joe Manchin of West Virginia, Bill Nelson of Florida, and Claire McCaskill of Missouri “tied up from campaigning,” a Republican donor told the Washington Examiner, relaying what Short communicated.

The meeting, organized by the National Republican Senatorial Committee, the Senate GOP campaign arm, was not a fundraiser. It was made available to some major Republican donors but no money was solicited in exchange for attending, the contributor said.

McConnell’s leadership office did not dispute Short’s preview of his spring and summer floor strategy to the group of donors.

“Sen. McConnell has been very clear that confirming the president’s nominees is and will remain a top priority for the Senate as was demonstrated last week,” said Antonia Ferrier, a spokeswoman for the majority leader.

Republicans have charged Democrats with unreasonable obstruction of Trump’s judicial and executive branch nominees. Democrats, arguing the president’s picks are unqualified or ideologically unacceptable, have demanded the full amount of debate time allowed under Senate rules to slow the confirmation process.

Last week, McConnell threatened Democrats with a weekend floor session if they did not ease the confirmation of a group of Trump nominees. The Democrats ultimately relented and no weekend session was necessary. Expect more of the same from McConnell in the weeks and months ahead.

This approach could assuage a GOP base that believes Senate Republicans have been too passive in pushing Trump’s nominees past Democratic obstruction. Action on this front could help motivate the party’s committed voters, who are particularly supportive of the president, to turn out in the midterm.

“The delay and obstruction tactics are historic,” Sen. Cory Gardner of Colorado, the NRSC chairman, said. “We have to clear the backlog of nominations. That means we are here — that means we stay here; we should stay here. We’re here as long as it takes to get the job done.”

Trump is broadly unpopular in national polling averages. But in red states like North Dakota, West Virginia, Florida, Missouri, and Montana, where Democratic Sen. Jon Tester is up for re-election, voters are satisfied with the president’s leadership, putting incumbent Democrats who have largely opposed him on the defensive. Only one incumbent Republican, Sen. Dean Heller of Nevada, stands to suffer from campaign schedule truncated by a busier Capitol Hill schedule.

With 49 seats in the Senate, Democrats are just shy of the votes they need to block Trump’s picks, which only need 51 votes to pass. But the filibuster is still operable, and Democrats have tended to use all of the debate time allotted to them under that parliamentary rule to slow the confirmation of the president’s judicial and executive branch hires.