Impeachment is the only answer. The GOP controls the House and the House has the sole power of impeachment.
No one is going to impeach this guy unless they find something that is undeniably incriminating of some sort of federal offense. The Republicans don’t have the political power or will to challenge this guy without fear of damaging their own political reputations. Second, an impeachment would be fruitless because the Democrats will rally the wagons in the Senate to prevent it from going any further.