I haven't seen any language saying actings can participate.
So all it would take is 8 of the below 15 plus Pence. The highlighted ones would be the most likely candidates.
- Secretary of State Mike Pompeo
- Secretary of the Treasury Steve Mnuchin
- Acting Secretary of Defense Chris Miller
- Acting Attorney General Jeffrey Rosen
- Secretary of the Interior David Bernhardt
- Secretary of Agriculture Sonny Perdue
- Secretary of Commerce Wilbur Ross
- Secretary of Labor Eugene Scalia
- Health and Human Services Secretary Alex Azar
- Housing and Urban Development Secretary Ben Carson
- Secretary of Transportation Elaine Chao
- Secretary of Education Betsy DeVos
- Secretary of Energy Dan Brouilette
- Secretary of Veterans’ Affairs Robert Wilkie
- Acting Secretary of Homeland Security Chad Wolf
The only problem is Trump could drag the whole thing out since after 8 plus Pence were to vote to get rid, Congress would ave to vote, then Trump would get a rebuttal, then Congress would have to vote again after considering his response. All of that could take weeks.