Is their protection from the Supreme Court?

Hartmann answers yes, indeed there is: Court stripping. Per Article 3, Section 2 of the Constitution:

"The Supreme Court shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make."

He provides a history of how this has been done repeatedly in the past. Even Chief Justice Roberts has previously argued for it with copious research and legal citations. All Congress has to do when writing legislation is to put therein a passage saying the Court has no jurisdiction over it.

One thing though. A similar issue is coming before the Court on the independent state legislature theory (ISLT). Proponents want their legislatures to decide elections regardless of the votes and prohibit any court from overturning their decision. If the Supremes agree to it then not even they can weigh in on their election criminality.

It seems the above Constitutional provision already gives legislatures this power and the ISLT is another way to strengthen this position so that it is beyond any judicial reproach, including the Supreme purview.