Question: Who is in charge if president is impeached?
Disambiguated questions and answers: question: Who is in charge of the  Senate trial if the US president is impeached?
Who is in charge of deciding whether to remove the US president if the president is impeached?
What says who is in charge if the president is impeached and removed?
answer: Chief Justice
Senate
United States presidential line of succession
Natural Questions answer: vice president (from the Wikipedia article "United States presidential line of succession")