Republican frontrunner Donald Trump loves to claim he is telling it like it is, but a new video from fellow Republican Rand Paul says Trump's record tells a different story.

The attack ad, launched on YouTube, shows quotes from Trump on issues ranging from Republicans being "too crazy right" to calls for universal healthcare and praise for Hillary Clinton.

"In many cases I probably identify more as a Democrat," Trump says in one clip. In another Trump says the economy does better under Democrats.

"I'm a liberal on healthcare," Trump says. "I love universal," he says when asked about universal health coverage which normally means a government-run system.

After close to a minute of quotes that could be troublesome from Trump with conservative-minded Republicans, the video switches over to praising Rand Paul.

"Defeat the Washington machine with a proven conservative and real reformer," read the words on the screen before a series of clips from Paul speeches are played.

"In order to restore America," Paul says, "We cannot, we must not dilute our message or give up on our principles."

Paul has worked hard to portray himself as the defender of the Constitution and the Bill of Rights. He has also tried to bridge from the hardcore and motivated libertarian base that his father built up to the broader conservative base of the Republican party.

The video may be the strongest attack against Trump launched by another candidate and stands in contrast to Ted Cruz's comments that it was "foolish" to criticize Trump and his supporters.