As federal employees braced for their first missed paychecks starting Friday, tension over the government shutdown reached a fever pitch, with House Majority Leader Steny H. Hoyer equating forcing people to work without pay to slavery. 

Speaking Thursday to a rally of unionized federal employees and their supporters outside the AFL-CIO’s headquarters, the Maryland Democrat spoke of the “440,000 people that are being asked to work with no pay,” adding, “You know, back in the 1860s, they talked about working with no pay.”

Hoyer was a featured speaker along with senators from Maryland and Virginia, home to many of the federal workers in and around the nation’s capital.

“I want to thank my friends in organized labor. Through history, many have been injured, many went without. Many walked the line, so that workers would get fairness,” Hoyer said. “That’s all we are asking, Mr. President. Fairness for our federal employees and fairness for the American people. Open up their government.”

Watch: Trump says no sign of GOP disunity, may still declare national emergency

The rally outside the union headquarters came after animated exchanges on the floor between Maryland Democratic Sens. Benjamin L. Cardin and Chris Van Hollen and Senate Majority Leader Mitch McConnell, with the Kentucky Republican expressing frustration that Democrats were blocking other bipartisan legislation from getting to the floor during the shutdown.

Democrats have blocked McConnell’s efforts to limit debate on a package of foreign policy bills held over from the 115th Congress that were introduced together by Florida GOP Sen. Marco Rubio. That includes both support for Israel and new sanctions against Syria.

In opening the floor Thursday morning, McConnell decried Democrats for not negotiating with President Donald Trump on border wall funding, a day after Trump literally walked out of a meeting with leaders including Speaker Nancy Pelosi of California and Senate Minority Leader Charles E. Schumer of New York.

“Let’s call this what it is. A flip-flop that is not based in principle, or in evidence, but solely in the fact that President Trump is the occupant of the White House. Republicans support the president’s commonsense request,” McConnell said.

But Democrats are criticizing McConnell for what they view as a flip-flop of his own, since the Senate passed a clean continuing resolution providing funding through Feb. 8, for the quarter of the government now closed, back in December. McConnell has said he will not bring that measure back because it would not get a presidential signature.

Outside the AFL-CIO, Virginia Sen. Mark Warner suggested that even a Trump veto threat should not be an excuse.

“Mitch McConnell said we can’t do anything that the president won’t sign. Well, I would point out that the Constitution says that the Congress is an independent branch of government,” the Democratic senator said. “The Constitution of the United States in Article I, Section 7, Clause 2, says the Congress can override the president with two-thirds vote.”