Instead of spending money on negative ads against GOP front runner Donald Trump, an outside political group that backs Jeb Bush is out with a new ad that goes after Marco Rubio on the hot button issue of immigration.

"Marco Rubio - just another Washington politician you can't trust," the ad says, as it delivered a punch line for Bush.

"Jeb Bush, he's a leader," the narrator says.

But the Bush ad was quickly met with scorn from some in conservative circles, who accused Jeb Bush of being on all sides of the immigration issue over the years.

GOP strategist and political consultant Mike Murphy, who runs the Right to Rise Super PAC, pushed back against that talk.

Rubio's campaign was quick to respond as well, sending reporters a release that was titled, "Jeb Bush's Right to Hypocrisy."

"Jeb Bush and his establishment allies are trying to buy this election and they know Marco is standing in their way," said Rubio spokesman Alex Conant.

Bush has tried once before to go after Rubio, attacking him during the third GOP debate - but that fell flat.