The impeachment hope rests on the belief that Mueller will find something out that is so extraordinarily bad about the President that almost half of the Republicans in the Senate will vote to remove Trump from office. To hold out hope that will happen is to believe that Republicans in positions of leadership do not already know about Trump’s involvement in Russia and will be shocked when they find out, but given the last two years that is not plausible. The only way Republican senators will vote to remove Trump is if their constituents demand it, but many Republican senators come from strongly red states where Trump is still quite popular.