Hardly...there are legal "remedies" when when Mueller goes beyond the scope of the declared investigation....Mueller is not immune to the rule of law because he calls himself a "special" independent (we all know...THE PEOPLE know that is not true) investigator/prosecutor.
No where in the original declaration/mission statement does it give Mueller the power to change the scope of the investigation arbitrarily to include investigating the MONEY from 10 years past . What? Do the democrats have the magical power to see into the future and know that Mr. Trump the real estate developer was going to be president in 10 years? This is called "mission creeping" authority...something the Clinton democrats bitched about when Slick was under investigation...it was not allowed then and it will not stand today.
There is DOJ precedent that's been around since 1973 (44 years)..... Mueller nor any "normal citizen" can criminally prosecute a sitting president...even for a crime. FYI: its unconstitutional. These idiots are just that...idiots. The president has the constitutional authority as the Chief Law Enforcement Officer of the land to PARDON or FIRE who he will....even Mueller (if he so wished) it would be no crime under the constitution, it might make him un-electable....but its not a crime. This dog and phony show "might" recommend impeachment...but that will not happen as the democrats don't have the political power. Slick willy was impeached but not convicted or removed from office and he was caught red handed breaking federal law (a crime) that crime...lying under oath. I said the same thing then....its nothing but a political show. And guess what? The republicans that put on the show? Lost control of congress. The democrats can't be reduced much more...but they can find the republicans with a super majority over this dog and phony show.
Lets enjoy the continued "circus".

While Trump continues to drain the swamp with his magic pen power.
The Precedent:
https://biotech.law.lsu.edu/blaw/olc/sitting_president.htm
The conclusion of the DOJ considering both Nixon and Clinton: "The department of justice concluded that the indictment (for any crime) would unduly interfere with the ability of the executive branch (remember that separation of power..thingy?) to preform its constitutional duties.........."