Republican Sen. Ron Johnson of Wisconsin has tested positive for coronavirus after being exposed to someone with the virus earlier this week, according to his spokesman, making him the third GOP senator to test positive in 24 hours and threatening the quick confirmation prospects of Judge Amy Coney Barrett to the Supreme Court. Sens. Mike Lee of Utah and Thom Tillis of North Carolina, who sit on the Judiciary Committee, tested positive for Covid-19 on Friday -- just days after attending a White House event where President Donald Trump nominated Barrett. Multiple attendees of that event, including Trump, have tested positive in the week since the ceremony, which featured many people not wearing masks and not observing social distancing protocols. Johnson did not attend the Barrett nomination ceremony — where several people appeared to have been exposed to the virus — because he was quarantining from a prior exposure, during which he twice tested negative for the virus, according to the spokesman. Unlike Democratic senators, Senate Republicans meet three times a week for lunch. And while they sit in a large room, they remove their masks to eat and to speak. Johnson, Lee and Tillis all attended Senate GOP lunches this week. If the three senators remain out this month, it would effectively prevent Barrett from being confirmed to the Supreme Court until they return, which could be after Election Day during a lame-duck session. A lame-duck confirmation is a situation that GOP leaders are eager to avoid in case they lose control of the chamber next month. On Saturday afternoon, Senate Majority Leader Mitch McConnell announced that Senate floor activity would be delayed until October 19, though committee work could continue. That adjustment to the schedule would require agreement from the Democrats for unanimous consent. CNN has reached out to Senate Minority Leader Chuck Schumer. Republicans are worried about getting enough votes to confirm a nominee in a lame-duck session after the election if they lose their majority -- and the White House -- and Democrats prepare to take power in January. The fear is that one or two GOP senators may break ranks after seeing the election results and citing the will of the voters. Already, Sens. Susan Collins of Maine and Lisa Murkowski of Alaska have indicated they are ''no'' votes if the confirmation vote happens before the election, and could vote against a nominee in a lame-duck session as well. With a 53-47 Senate majority, Republicans can not afford to lose more than three senators in order to get the nomination confirmed. Senate Judiciary Chairman Lindsey Graham told CNN on Friday night that he planned to push forward and hold hearings beginning October 12 and would try to get the nomination approved by his panel by October 22. Graham released a statement Saturday afternoon repeating his commitment to that schedule.