Former Commerce Department official Ro KhannaRohit (Ro) KhannaTrump button tweet sparks backlash House Dem calls for bill to restrict Trump's ability to launch preemptive nukes Hundreds demand US, UK, French action to end Yemen civil war MORE (D) knocks Rep. Mike Honda (D-Calif.) in his newest ad, the first time Khana has publicly gone negative against Honda in their race.

"First, Mike Honda stubbornly refused all debates. Now Honda's slinging mud, launching false attacks. Isn't it time to put the old politics aside?" the ad says, referencing a recent mail piece in which Khanna attacked Honda.

The spot then touts newspaper endorsements of Khanna, saying he's "for our future."

The well-funded Khanna is looking to make the runoff against Honda in the all-party June primary in the heavily Democratic district.