Donald Trump just gave out a rival presidential candidate's phone number, because Donald Trump

Donald Trump is giving us more and more reasons to think that he really is a Democrat sleeper agent.

But no: the "the patron saint of topical comedians" really has just put his foot in his mouth again by publicly handing out the personal phone number of an opponent in the Republican presidential race, South Carolina senator Lindsey Graham.

Trump was at a campaign rally in Graham's home state on Tuesday when he called the sitting senator an "idiot" and doxxed him by telling the crowd to try his phone number. A Politico reporter did, and Graham picked up, although his connection later jammed after he was flooded with calls from Trump supporters.

Graham recently called Trump a "jackass" for claiming that Republican former presidential candidate John McCain was "not a war hero" for spending five years as a prisoner of war in Vietnam.

So far in his campaign Trump's also managed to take pot shots at Mexican immigrants and gay people. Astoundingly, though, the business mogul is still polling at 24 per cent among Republican voters, ahead of Scott Walker (13 per cent) and Jeb Bush (12 per cent).

If there still is a line, when is Trump going to cross it?

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