Two of the three senators who have now tested positive for the virus, Mike Lee of Utah and Thom Tillis of North Carolina, were at the Barrett announcement and serve on the Senate Judiciary Committee that will consider her nomination, further complicating a confirmation drive that was already testing speed limits and a razor-thin majority to get done before the election, as Mr. Trump has insisted.
Mr. Johnson, the third senator now infected, was not at the event because he was quarantining from a previous exposure to someone with the virus. He emerged from 14 days of quarantine after testing negative and returned to Washington on Tuesday, his office said, but attended lunch with other Senate Republicans that put him in the same room with Mr. Lee and Mr. Tillis. He was tested again on Friday.
“This test came back positive,” Ben Voelkel, a spokesman for the senator, said in a statement. “Senator Johnson feels healthy and is not experiencing symptoms. He will remain isolated until given the all-clear by his doctor.”
If all three Republicans were unable to vote, then Senator Mitch McConnell, the Republican majority leader from Kentucky, would not have enough support to force through confirmation of Judge Barrett. Because two moderate Republican senators, Susan Collins of Maine and Lisa Murkowski of Alaska, have already indicated that they oppose installing a new justice before the election, that would leave Mr. McConnell with 48 Republicans to 49 Democrats and the two dissenting Republicans.
But even as Mr. McConnell said on Saturday that the full chamber would not meet this coming week as planned, Republican leaders vowed to push ahead with the confirmation on the hope that the infected senators would not get sick and therefore be able to return in time for a pre-election vote. Senator Lindsey Graham, Republican of South Carolina and chairman of the Judiciary Committee, issued a statement saying the panel would proceed with plans to meet on Oct. 12 to begin considering Judge Barrett’s nomination.
But Republicans could need contingency plans depending on whether the three senators who tested positive get sick. One option being discussed was holding the Judiciary Committee vote in the Senate chamber with the infected senators perched in the galleries overlooking the floor, far from their colleagues.
The president’s illness forced him off the campaign trail with just a month until the election on Nov. 3. Mr. Trump’s events have been canceled, as have those of his immediate family for the moment while they confirm negative test results, leaving it to Mr. Pence, who has tested negative for the virus, to pick up the burden of the contest against former Vice President Joseph R. Biden Jr., the Democratic nominee.