He was born here, of two US citizens, Cruz and Rubio were not.
Cruz and Rubio have never “identified as a Democrat”. Both are eligible to be president, and both can beat Clinton or Sanders.
Trump is the worst of the candidates to put up against Clinton. He has high negatives with women, and his past support and friendship with the Clintons will make any current criticism seem disingenuous.
Putting Trump against Clinton is like putting Romney up against ObamaCare. They can say the right words but no one believes them.