"...colluded with the Russkies and forced Americans to vote for him."
No.  No one believes he "forced" anyone to vote for him.  There is concern that he and members of his then campaign team and future cabinet did have contacts with the Russians and lied about it.  That is essentially what Flynn did and whether Trump or his minions lie about it, the "lying" becomes the issue because it now looks like something illegal happened and is being covered up.  If Trump is actively trying to suppress an investigation by firing someone like Comey, he may be "obstructing justice" which is a criminal act.  In any event, he appears to be lying about everything with a different lie daily.  At some point, he will lose the confidence not just of other politicians but of even his own voters, and at that point he becomes a lame duck and unable to achieve any of his administration's goals.  He needs to come clean and get this behind him or get out.  Obfuscation will fail here.