The Founders created the impeachment process without consideration for political parties. They naively assumed Congress would act in accordance with the Constitution and standard jurisprudence with no regard for ideology. While it hasn't always been this way, there are really only two parties that matter at the Federal level. The House of Representatives, which is responsible for determining whether a trial is appropriate (similar to a Grand Jury), is controlled by Republicans. They won't even consider holding impeachment hearings, let alone recommend a trial in the Senate. The Senate, also controlled by Republicans, would likely do the same thing they did twice during his first term, which is essentially nothing.