Nothing to do with Citizens United. There is no “independent political spending.”
It would fail on the basis of the First Amendment. The courts have ruled on forced speech and forced assembly. And political affiliation is not a federally protected class, so there isn’t even wiggle room.
The Supreme Court ruled that the First Amendment right to free speech applies to corporations and thus the government cannot limit their political spending.
Now that corporations have codified Political First Amendment rights, this proposed law would clearly fail a SCOTUS challenge.
Citizens United reaffirmed corporate personhood and the Constitution’s protection of all persons, natural or legal. But that is old case law.
The novel part was ruling that “independent political spending” counts as First Amendment protected speech.
This law would never stand a Supreme Court challenge thanks in part to Citizens United.