a) You need 2/3 of senators to vote to convict, so you would need ~20 Republicans to get on board. b) Impeachment is a political action; plenty of politicians

a) You need 2/3 of senators to vote to convict, so you would need ~20 Republicans to get on board. b) Impeachment is a political action; plenty of politicians can disagree with portions of their party's legislature enough to vote against it without saying "I'd like to burn down my party's control of the government (and thereby my career) over this".