The initiative, known as the "Texas Offense," is a push to support former NFL linebacker and attorney Democratic US Congressman Colin Allred, who is working to unseat Cruz.
"On Nov. 5, I'm going to defeat Ted Cruz," Allred promised the White Oak Music Hall crowd on Sunday.
SEE HERE: This Week in Texas: 1 on 1 with Ted Cruz and Colin Allred and insights on Texas Congress race
"In 100 days, we can say adios to Cruz and send him on a one-way flight to Cancun," State Senator Carol Alvarado told the audience.
However, polls have widely indicated that Cruz, who has held onto his seat for the last 12 years, is the frontrunner. Cruz's campaign has about $2 million more cash than Allred's.
Yet Allred continues to outfundraise Cruz's previous challenger, Beto O'Rourke. O'Rourke, whose campaign garnered much national attention, came close to unseating Cruz. He lost the race by three percentage points.
"I'm very hopeful that we actually will (defeat Cruz.) I think there's a lot of excitement," Susan Pollard from Moms Demand Action said.
Gun safety was among the top issues Allred supporters told ABC13 that drove them to the rally, along with border policy and women's reproductive rights.
Allred's remarks were disrupted twice by those protesting the war in Gaza. Earlier this year, Allred split from the Texas Democratic Party when he did not join their call for a ceasefire. Instead, he has supported Israel continuing the war while stating they have an obligation to follow international law.
RELATED: US Senate candidates Ted Cruz and Colin Allred sit down with ABC13, discuss campaigns
Senate candidates Ted Cruz and Colin Allred discuss campaigns
Speakers at the event appeared to work to capitalize on momentum from Democratic presidential candidate Kamala Harris' nomination. In recent weeks, several Democrats have publicly expressed concern that President Biden's low polling numbers could drag down competitive state races.
Precinct One Commissioner Adrian Garcia referred to the county as "Kamala 'Harris' County," - a term that was echoed throughout the afternoon.
Earlier in the week, Cruz told ABC13 that Allred "bears full responsibility for the disastrous policies of Joe Biden and Kamala Harris."
In his remarks, he accused Allred of being "extremely liberal" and "radical."
Data fromVoteviewranks Allred as the 69th most liberal democratic US Representative out of more than 200. Voteview is an academic entity that ranks members of Congress from left to right for their role, and it is called vote behavior.
Cruz also slammed Allred for voting "100 percent with Nancy Pelosi" during his first four years in Congress.
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