I hate this conflation of things like SCOTUS nominations with criminal trials. Santos is afforded due process in his criminal trial. But the House doesn't have to wait for a conviction. It can judge the evidence against him. If Porter thinks it is appropriate for him to resign, she should think it appropriate to expel him. It is precisely because he won't resign that the House should have the right to expel him.
The first expulsion from Congress was William Blount. He was expelled from the Senate within five days of the discovery of his conspiracy to help Britain take over Spanish-controlled Louisiana and Florida. He was never convicted.
Both Santos and Menendez completely harm the integrity of Congress. It is utterly absurd to not expel them given what they are accused of doing in indictments.
The two thirds requirement already accounts for the gravity of expulsion. It is hard to get two thirds of the House to agree on anything.