In the Twitter war no one asked for, Donald Trump Jr. and California Sen. Kamala Harris are trying to determine what the real "joke" is.

The exchange started Friday night when Trump Jr. tweeted a video of the 2020 candidate laughing at an event in January.

"Why is @KamalaHarris the only person that laughs at her jokes... always way to long and way too hard?" he wrote alongside the video. "The most disingenuous person in politics... after Hillary."

Harris (or perhaps her campaign staff) responded to Trump Jr. with, "You wouldn't know a joke if one raised you."

Not long after Harris called his father a joke, Trump Jr. responded and made fun of her poll numbers.

"Based on your tanking poll numbers, what’s definitely a joke is your entire campaign (laughing emoji) Yikes!" he wrote.

The president's son attached a screen shot of the latest RealClearPolitics polling averages for national polls in the 2020 Democratic primaries.

Former Vice President Joe Biden leads the field with a polling average of 27.8 percent, and is followed by Massachusetts Senator Elizabeth Warren at 26 percent. Vermont Senator Bernie Sanders is in third place with a polling average of 15.2 percent, and in fourth place is South Bend Mayor Pete Buttigieg at 5 percent.

Harris is in fifth place behind Buttigieg at 4.5 percent, a noticeable tumble from when she was polling alongside Biden, Warren and Sanders over the summer.

The California senator has not responded to Trump Jr.'s polling averages tweet.

Eric Ting is an SFGATE digital reporter. Email: [email protected] | Twitter:@_ericting