The courts, with judicial cowardice, refused to hear a case brought after both the election and that person’s inauguration.
It only takes 1 member of Congress to halt the election result. No member of Congress objected to the election or to Obama’s inauguration.
The black robes refused to entertain a suit much less remove a sitting President after so many opportunities for protest were passed by.
You can be sure that the Democrats learned that lesson well and will not let any ineligible Republican candidates progress. They will instead choose the timing that results in the most damage to the Republican nomination process.
It takes two, one from the House and one from the Senate, to raise an objection. At that point, the respective bodies retire to their chambers and vote. It takes a majority to uphold the objection.
-- ... the Democrats learned that lesson well and will not let any ineligible Republican candidates progress. --
I wouldn't be so sure of that. The parties are in lockstep unison on the mission of eroding national identity. I think the Courts are in on it too.