Both candidates lobbed attacks throughout, taking more aggressive stances as the race enters the final stretch and Democrats try to keep their fledgling hopes of re-taking the Senate alive despite a hard host of races in many states President Donald Trump won handily in 2016.
During a segment on climate change and oil taxes: "Senator Cruz is not going to be honest with you", O'Rourke said. He's going to make up positions and votes that I've never held, ' he said during the debate in a San Antonio television studio. "It's why the president called him "Lyin" Ted, ' and why the nickname stuck".
Cruz's comment was a reference to O'Rourke's past comments that he supported impeaching Trump.
Democrats have long dreamed about a growing Hispanic population helping to flip Texas from red to blue and shaking up the electoral map.
O'Rourke has shattered fundraising records and attracted national attention, but polls that once showed him staying within striking distance now have Cruz ahead. A Democrat hasn't won statewide in Texas in 24 years.
"Well it's clear Congressman O'Rourke's pollsters told him to come out on the attack", Cruz said.
O'Rourke also faulted Cruz for leading the 2013 federal government shutdown, for missing votes in Washington and for campaigning in Iowa to further his presidential ambitions rather than spending more time in Texas.
Piers Morgan mocks Daniel Craig's baby carrier, gets manhood lesson
The 007 star was pictured carrying his youngest child in the traditional style baby carrier when he was photographed by paparazzi. Others straight-out skewered Morgan, while lots of dads posted sweet photos of themselves proudly carrying their own babies.
"Really interesting to hear you talk about a partisan circus after your last six years in the U.S. Senate", O'Rourke said to laughter in the audience.
A question over trade led to a battle about party control in Congress.
In response, O'Rourke said Cruz is all talk and no action about his relationship with the president and questioned where the results are.
Minutes later, he added: "Ted Cruz has done so much for Texas, including massive cuts in taxes and regulations-which has brought Texas to the best numbers in the history of the state".
Cruz kept O'Rourke on the defensive when they debated last month in Dallas, and O'Rourke, who had maintained a feel-good message, has promised a sharper tone Tuesday night in San Antonio.
But O'Rourke's feel-good message exposed vulnerability during the first debate, on September 21.
O'Rourke is trailing behind Cruz in the latest polls, despite his record-setting $38 million in campaign funds last quarter.