White House spokesman Josh Earnest played down the prospect of major firings.
"At this point, I don't anticipate that will happen," he told a briefing. He said a key factor driving the election was
"frustration with the failure of Washington, D.C., to put in place policies that are helpful to middle-class families."
Vice President Joe Biden told CNN in an interview broadcast on Monday that he expected Democrats would hold the Senate and dismissed suggestions that the White House would have to change the way it does business.
Voters elect 36 senators, all 435 members of the House of Representatives and 36 state governors on Tuesday. Control of the Senate may not be clear, though, for some weeks, depending on the outcomes of races in Georgia and Louisiana that could spur runoffs.