Sen. Kamala Harris (D-CA) took aim at Donald Trump Jr. on Friday for his description of her as “the most disingenuous person in politics… after Hillary.” She responded to the president’s eldest son by tweeting, “You wouldn’t know a joke if one raised you.”

On Friday, Donald Jr. tweeted a video of the California senator and presidential hopeful awkwardly laughing at herself during a Q&A.

“Why is @KamalaHarris the only person that laughs at her jokes… always way to [sic] long and way too hard?” Trump asked. “The most disingenuous person in politics… after Hillary”:

Why is @KamalaHarris the only person that laughs at her jokes… always way to long and way too hard? The most disingenuous person in politics… after Hillary. pic.twitter.com/elskW29XeP — Donald Trump Jr. (@DonaldJTrumpJr) October 12, 2019

“You wouldn’t know a joke if one raised you,” Harris tweeted back:

You wouldn’t know a joke if one raised you. https://t.co/zUV3MLkmVm — Kamala Harris (@KamalaHarris) October 12, 2019

Trump responded with a screenshot of the Real Clear Politics average, which over the past few weeks has shown Harris steadily sinking in the polls.

“Based on your tanking poll numbers, what’s definitely a joke is your entire campaign,” Trump wrote, adding, “Yikes!”:

Based on your tanking poll numbers, what’s definitely a joke is your entire campaign Yikes! https://t.co/3vkxo5gUyO pic.twitter.com/oKMCKuscBR — Donald Trump Jr. (@DonaldJTrumpJr) October 12, 2019

The current Real Clear Politics average shows Mayor Pete Buttigieg (D) overtaking Harris’s fourth-place position, dropping the California lawmaker to fifth place with just 4.5 percent support, more than 20 percentage points short of both Joe Biden (D) and Sen. Elizabeth Warren (D-MA).