Can conservatives trust Donald Trump?

That's the question posed to Iowans in a new attack ad against the Republican frontrunner. The attack ad interrogates of the central tenets of Donald Trump's campaign since the get-go: illegal immigration.

Our Principles PAC - youtu.be

The ad, funded by the Our Principles PAC — a conservative group headed by a former top aid for Mitt Romney's 2008 presidential campaign — calls into question just how serious the candidate is on curtailing illegal immigration, accusing him of profiting off of cheap immigrant labor. Trump's brash remarks on immigrants have gained him sensational public attention: in a speech announcing his candidacy in June, the businessman called Mexicans "rapists." He has since said that all 11 million undocumented immigrants would be immediately deported under a Trump White House.

"Donald Trump is skipping the last debate before the Iowa caucuses," the ad begins. "Why? Trump can’t handle tough questions, like why he’d let millions of illegal immigrants stay in America and even supports a pathway to citizenship."

Our Principles PAC - youtube.com

The ad calls up a number of clips in which Trump apparently voices his support for amnesty for undocumented immigrants and even a pathway to citizenship. The ad also accuses the businessman of hiring undocumented workers to work on Trump construction projects.

Our Principles PAC - youtube.com

The spot — part of a seven-figure ad buy by the PAC — represents a last-ditch attempt to throw a wrench in the businessman's otherwise sturdy political standing just days before the pivotal Iowa caucus vote. Though Trump has consistently lead national and state polls, observers are expecting a fierce competition in the Iowa caucus from Ted Cruz.

Previous ads by the PAC questioned Trump's position on key issues like abortion and health-care. Watch the full ad below: