I don't think it'll cost Trump the election, but even if it does, the right lifetime appointee on the SCOTUS can be far more effective than a 4 year POTUS with a divided or fully opposition congress.
Why are judges partisan?
Yes, why? They shouldn't be. They should be interpreting laws and and defending the Constitution. But the leftist judges have systematically legislated from the bench and reinterpreted the Constitution to say what they wanted it to say.
Judges should not be partisan