LAGUNA BEACH, Calif. — The Democratic Congressional Campaign Committee is teaming up with businessman Harley Rouda on a joint television ad two weeks before the critical California primary.

Rouda is the DCCC-backed candidate in the 48th district held by Republican Rep. Dana Rohrabacher. The ad, shared first with Roll Call, is part of a Democratic push to mobilize voters to vote in the June 5 primary.

“Washington extremists are moving us backwards,” the narrator says over an image of Speaker Paul D. Ryan. “President Obama fought to move us forward. Democrats and Harley Rouda will do the same.”

The 30-second hybrid ad, a joint effort by the DCCC and the Rouda campaign, is part of a $400,000 ad buy in the Los Angeles media market. It hits the airwaves Tuesday and will be seen this week on broadcast and cable.

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The DCCC is backing Rouda even though the California Democratic Party endorsed stem cell researcher Hans Keirstead in the 48th District. The committee added Rouda to its “Red to Blue” program for strong challengers, in part because of his grass-roots support.

Rouda in an interview after a rally here Sunday called the state party’s backing of Keirstead  a “mistake.” He said that move emboldened grass-roots activists to back his campaign.

“They felt that their vote had been usurped and became even more active and dedicated and committed to making sure our campaign had the success we believe it should have,” Rouda said.

Indivisible Orange County 48, which hosted Sunday morning’s rally at the main beach here, has also endorsed Rouda. The group’s chairman, Aaron McCall, said the state party endorsement of Keirstead was made too early. 

McCall mentioned the DCCC’s endorsement of Rouda as he addressed the crowd at the beach on a misty morning. And he implored Rouda supporters to engage in get-out-the-vote efforts, which is especially important in the jungle primary.

Under California rules, all candidates will run on a single ballot with the top two vote-getters advancing to the general election, regardless of party. With multiple Democrats running in the 48th, there is concern they could split the Democratic vote, leaving two Republicans, Rohrabacher and Scott Baugh, a former Orange County GOP chairman, to advance to November.

“We have to fight, fight, fight to give Harley a chance in November because we can be locked out with just Baugh and Rohrabacher, and we don’t want that,” McCall said.

Rouda, a former Republican, said he hopes to get through the primary by appealing to Democrats as well as GOP moderates and voters who do not declare a party preference.

But the joint ad with the DCCC is aimed at Democrats. It says the party plan includes “health care access expanded, Planned Parenthood protected, women’s equality now … fighting the NRA, banning assault weapons, tougher background checks, and combatting climate change.”

The 48th District is one of seven GOP-held seats in California that Hillary Clinton carried in 2016, backing the Democratic presidential nominee by 2 points. Inside Elections with Nathan L. Gonzales rates the general election race Tilts Republican.