The google machine says he needs to be on the floor to cast his vote for a final bill. I think they should change this rule. Our representatives should only be physically in Washington a few weeks out of the month for a week at a time to gladhand and attend the State of the Union address. Otheriwse all business should be conducted from the district or state he/she/it is representing and get them out of the bubble that is Washington.
Then wheel him in .... :^)
However they find it much easier to be paid off by lobbyists in Washington.