SAN ANTONIO — Rep. Beto O'Rourke, D-Texas, went on the attack against Sen. Ted Cruz, R-Texas, in Tuesday's debate as part of a last ditch effort to revive his flagging Senate campaign.

On multiple occasions, O'Rourke went on the offensive against Cruz, calling the Texas Republican "dishonest" during a back-and-forth on climate change, even invoking the nickname President Trump gave Cruz during the 2016 GOP primary campaign.

“Senator Cruz is not going to be honest with you," O'Rourke said when asked about climate change. "He’s dishonest. It’s why the president called him 'Lyin’ Ted,' and it’s why the nickname stuck. Because it’s true.”

Cruz responded that it was "clear" O'Rourke's pollsters and consultants "told him to come out on the attack" before counter-punching, pointing to O'Rourke's call to raise the tax on a barrel of oil by $10.

Twice in the hour-long event, O'Rourke accused Cruz of ineffectiveness, particularly over his inability to stop rounds of tariffs imposed by the Trump administration despite his proximity to the president. Cruz responded that O'Rourke wanted to impeach Trump, which he said would result in a "partisan circus."

"It's really interesting to hear you talk about a partisan circus after your last six years in the U.S. Senate," O'Rourke said. "You are all talk and no action."

The El Paso congressman also used the line to hit Cruz for not supporting the Violence Against Women Act before arguing that he has been an absentee senator.

"You've got somebody who left the state of Texas within a year of being elected to represent all of us to run for another office," O'Rourke said. "Hasn't been to all the counties of Texas but has been to all 99 [counties] of Iowa."

Cruz's team chalked the attacks up to O'Rourke trailing significantly with only three weeks until Election Day and less than a week before early voting commences in Texas. According to the latest RealClearPolitics average, Cruz leads O'Rourke by 7 points, up nearly 2.5 points in a week and a half.

[Also read: Beto O'Rourke won't share his $38M with fellow Democrats]

"When you're down ten [points], you better do something, right? You better change the conversation," Jeff Roe, Cruz's chief strategist, said after the debate. "When an unconventional candidate becomes conventional, that's typically when they get split like a cantaloupe, and I think that's what you'll see."

Roe noted that their latest internal poll shows Cruz up 11 points over the Democratic congressman. Over 50 percent of the total votes are expected to come during the two-week early voting period.

While O'Rourke attempted to score points with the barbs, Cruz was unfazed and caught O'Rourke flat-footed on multiple occasions, including during a back-and-forth on the congressman's vote against Hurricane Harvey aid last year, the second of two packages passed by Congress. O'Rourke, who voted for the first package, said that he does not regret the second vote.

"I don't [regret the vote]," O'Rourke said. "I'll always see what I can do, work with anyone anytime anywhere to do better for Texas. That was what I was trying to do."

One topic that did not come up was the $38.1 million haul O'Rourke posted during the third fundraising quarter. O'Rourke has nearly $23 million in cash on hand to Cruz's $11.3 million. Having raised $12 million, Cruz's team believes they have more than enough to compete for the final three weeks.

"We have enough money. I recall outspending a candidate in a race by $30 million and it not having a big impact," Roe said, referring to Trump's victory over Cruz over two years ago.

The debate comes just under a week ahead of Trump's planned visit to stump for Cruz next Monday in Houston, the senator's hometown, which his campaign expects to boost them in the race.

"It's great. I'm pumped. In the Houston market, a visit by the president will have a profound impact with turnout, motivation, excitement," Roe said. "We've been flooded since it was announced."

Roe added that the city and venue, the 8,000-seat NRG Arena that sits next to the Astrodome and NRG Stadium, home to the Houston Texans, were both chosen by the White House.