NASHVILLE, Tenn. — President Donald Trump slammed frequent foe Sen. John McCain, R-Ariz., who is battling brain cancer, for having voted against one of the measures that would have repealed Obamacare last year.

Speaking at a rally here, and referring to McCain without using his name, Trump said his efforts to scrap President Obama’s signature health care law were frustrated by the Arizona senator’s decision to give a thumbs-down to the bill on the Senate floor in July.

“We had…