And IMHO, he was not a natural born citizen of the US as required by the Constitution.
Assuming you meant Cruz and not Trump, why should the Democrats bring it up? There are more than enough Republicans willing to do that for them.
Yes, If Trump in the nominee and Cruz were a VP candidate, The dems will file a suit with a hack judge and try to get it up to the compromised judge Roberts on SCOTUS as fast as possible.