Democrats are doing their best to resurface the bitter feuds between President Donald Trump and Sen. Ted Cruz, as the Texas lawmaker fends off a strong Democratic challenge this fall.

One team of liberal activists is rolling out billboard trucks featuring Trump's tweets attacking Cruz.

And Democrats are sharing video clips of the two men viciously undermining each other during the 2016 campaign.

Sen. Ted Cruz and President Donald Trump have had a tumultuous relationship, to say the least.

But that is a history both men would like to forget. They need each other now, as Cruz faces an unexpectedly competitive challenge to his Texas seat in a race that could determine party control over the US Senate.

So Democratic activists are doing their best to remind Texas Republicans that it wasn't long ago that the president declared Cruz a "maniac," questioned his American citizenship and religious beliefs, promoted conspiracies about his father, threatened to "spill the beans" on his wife, Heidi (and attacked her physical appearance), and nicknamed him "Lyin' Ted" — not to mention asserting that Cruz had done "absolutely nothing" for his state.

Antonio Arellano, a Texan activist and Latino community organizer, recently teamed up with David Hogg, a survivor of the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, and a few other activists to raise money for an idea Arellano hatched: billboard trucks featuring Trump's tweets attacking Cruz.

After the group raised $9,760 through a GoFundMe page, they stopped accepting donations and prepared for the rollout, The Washington Post reported. The trucks carrying the billboards will hit the road in the red state on Thursday, Arellano tweeted last week.

Democrats are also spreading footage of Cruz's attacks on Trump from when he was a presidential candidate, which included calling Trump a "pathological liar," "utterly amoral," a "narcissist at a level I don't think this country's ever seen," and a "serial philanderer" during the 2016 campaign.

On Tuesday, Neera Tanden, president of the progressive think tank Center for American Progress, shared a video of the ultra-conservative senator calling the president a "sniveling coward" in March 2016, while insisting that Trump wouldn't be the party's presidential nominee.

"Everyone in Texas needs to see this," she wrote.

Since the election, relations between the two men have made a remarkable recovery. Trump announced via tweet last month that he'll hold a rally for Cruz in "the biggest stadium in Texas we can find" and called the senator's Democratic opponent, Rep. Beto O'Rourke, "a disaster for Texas."

Cruz, who was outraised two-to-one by O'Rourke last quarter, is also aggressively courting wealthy donors and conservative groups to send financial support to his campaign.

Last year, Trump described his evolution with Cruz as "like, dislike like."

The relationship between the two has indeed gone from friendly, to nasty, to apparently amicable again. While the men avoided taking shots at each other in the first months of their respective campaigns for the presidency, their relationship soured as the GOP primary narrowed.

"This man is a pathological liar. He doesn't know the difference between truth and lies," Cruz said after Trump alleged that Cruz's father was involved in President John F. Kennedy's assassination. "In a pattern that is straight out of a psychology text book, he accuses everyone of lying."