Incubation period is usually 2-3 days.
While it can happen, in most cases it’s 4-7. The most likely source of the infection was the event “honoring” Amy Coney Barrett, as all of the prominent people in the Trump administration who are now infected were there and sitting close together.
(Barrett herself had Covid earlier this year and recovered and is unlikely to be the actual source. Some people are blaming Kellyanne Conway because reporters started looking into things when her daughter reported that the entire Conway family was sick, but that’s basically blaming the parent of the messenger without proof.)