WASHINGTON — Senator Chuck Schumer, Democrat of New York and the majority leader, tested positive for the coronavirus on Sunday, forcing him into isolation just as the Senate was set to reconvene on Monday night after a two-week recess, and ahead of one of its last major work periods before the midterm elections.
Senator Richard Blumenthal, Democrat of Connecticut, announced on Monday that he, too, had tested positive and would be working remotely for the week.
And Senator Patrick J. Leahy, Democrat of Vermont, 82, who broke a hip last month in a fall at his home in McLean, Va., was still out recovering from surgery. Mr. Leahy’s spokesman, David Carle, said the senator would be “available for votes this week if necessary.”
Still, the three absences threatened to upend Democrats’ plans for a productive July in the evenly divided Senate, and were the latest reminders that the party’s bare-minimum majority is exceedingly precarious.
Democratic leaders had expected this week to finally confirm Steven M. Dettelbach, President Biden’s nominee to head of the Bureau of Alcohol, Tobacco, Firearms and Explosives, and Ashish Vazirani as a deputy under secretary of defense. They had also planned to vote on the confirmation of Michael S. Barr to serve as the Federal Reserve’s vice chair for supervision.
For now, Democrats are in wait-and-see mode on whether they will move forward on the confirmations, aides said. With the Senate evenly divided, assuming Republicans are fully in attendance and unanimously opposed, the absences among Democrats would mean they could not muster a majority to confirm any nominee along party lines.
But the nomination of Mr. Dettelbach was supported by two Republicans, Senators Rob Portman of Ohio and Susan Collins of Maine, giving him a potential path to confirmation even with some Democrats absent. Mr. Vazirani’s confirmation was considered uncontroversial, and also garnered some Republican support.
Democratic aides said the timing of Mr. Schumer’s bout with the coronavirus, his first since the start of the pandemic, could have been worse. While it made for a halting start after a two-week break, the Senate was not expected to do any substantial legislative work this week, including on Democrats’ tax and domestic spending package, which the party plans to try to revive this week and push through the Senate over Republican opposition.
Still, Monday was supposed to be the start of a five-week burst of activity before the Senate adjourns for its annual summer break in August, and the longest such stretch before the midterm elections in November.
The extended absence of Mr. Leahy, coupled with the coronavirus cases, underscored the fragility of the 50-50 majority in the Senate, where there is always a fear that any of the party’s half-dozen octogenarians could fall ill and suffer a prolonged absence that could imperil or delay Democratic legislation or presidential appointments that have no Republican support.
In February, Senator Ben Ray Luján, 49, Democrat of New Mexico, suffered a stroke. Although he recovered quickly, his illness served as a reminder that Democrats are never more than one sudden illness away from losing their working majority.
And while Covid cases in Congress appeared to have subsided somewhat in recent months, more lawmakers — like many other Americans — have recently been reporting cases as a new variant, the most transmissible yet, rips through the United States.
In the House, Representative Katie Porter, Democrat of California, said on Monday that she had tested positive after being exposed while working in her home state. Speaker Nancy Pelosi has extended proxy voting, which she instituted in the House at the beginning of the pandemic, through Aug. 12, permitting lawmakers to continue to vote remotely.
In the Senate, Democratic aides were eager to play down the significance of the post-recess absences and illnesses, and said business would continue almost as usual.
“Anyone who knows Leader Schumer knows that even if he’s not physically in the Capitol, through virtual meetings and his trademark flip phone, he will continue with his robust schedule and remain in near-constant contact with his colleagues,” his spokesman, Justin Goodman, said in a statement.