Donald Trump's rivals are scratching their heads over the seemingly unstoppable rise of the most un-presidential presidential candidate around.

The latest polls have him powering away from his Republican competition, on 26 percent support.

The next closest is Jeb Bush on 12, followed by Scott Walker on 11.

Republican consultant Ari Fleischer said those two however, are in a strong position.

"Their job should be to look presidential, to rise above Donald Trump, to really be the person that the Republican party wants to coalesce behind."