When there is no known evidence, there should be no investigation. This investigation is a fishing expedition.
Based on what we do know Mueller and his appointees should all recuse themselves as they have all demonstrated their bias.
American Thinker has an article on this subject:
The current disgraceful witch hunt being perpetrated against President Trump is a good example of why special prosecutors (or counsels) are a bad idea. No crime has been charged against anybody. No specific wrongdoing has been alleged. All we have heard are vague hints of collusion with Russia to meddle in an election. How, one might ask? Silence. A few lucky people who have been shown classified facts opine that there was some kind of Russian “meddling.” Yet investigating through ordinary channels is said to be inadequate. The Attorney General was virtually forced to recuse himself because he had a couple of trivial encounters with Russians during the campaign.
Make no mistake about it. The “honorable” Mr. Mueller seems to think his job description is to destroy the President by any means possible. That is wrong. That is un-American. That is an affront to the Constitution. It is hard enough to defend oneself against a concrete accusation. Here there is not even a potential accuser to bear false witness. Even unscrupulous fascist regimes usually come up with trumped up (sic) charges, but not our special prosecutor. Oh no, not him. He is too high and mighty to keep the public informed, other than by self-serving leaks. But then, there is no suspected crime being investigated. He ought to be ashamed of himself for participating in this farce. One can only hope that the federal bench scrutinizes subpoenas issued to Trump and his family for random information unrelated to Russian involvement in the election.