Candidates often use a snippet of something embarrassing that their opponent said in a past campaign. What you never see is a candidate running another candidate’s entire campaign ad as his or her own — but that’s what’s happening in the race for state insurance commissioner.

(Yes, we know what your next question is: “Who’s running?”)

Democratic state Sen. Ricardo Lara of Bell Gardens (Los Angeles County) is running an online ad that consists of a TV commercial that his opponent, Steve Poizner, ran in 2010 when he was a Republican running for governor.

In the ad, Poizner promised to cut “taxpayer-funded benefits” for “illegal immigrants.”

But Poizner is now running as an independent and would prefer that voters not be reminded of views he held waaaaay back in 2010 — many of which he says he no longer holds.

Political advertising expert Travis Ridout, a professor of political science at Washington State University and co-director of the Wesleyan Media Project, said he’s never seen a candidate do this before. He doubts it will be effective.

“The average viewer might be a bit confused,” he said. “They’re asking, ‘Why am I seeing an ad for governor?’ Maybe the (Lara) campaign is hoping that some people in the media write about it so more people can be reminded of (Poizner’s) former views.”

It worked on that level, at least.

Joe Garofoli is The San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli