Sen. Rand Paul, R-Ky., said his father was "one of the intellectual godfathers of the Tea Party."
"The revolution is working, we have infiltrated the Republican Party, and we will convert the Republican Party to defenders of liberty," he said.
And both Pauls threw their support behind Cruz, who is in a crowded GOP fight for the nomination to succeed Kay Bailey Hutchison in the U.S. Senate.
"You have a candidate in Ted Cruz, I hope you'll give him a chance, if you give him a chance you'll have a real hero from Texas and you need one, he understands the constitution and what it's about," Rand Paul said.
U.S. Rep. Ron Paul, who has made several appearances in Texas in recent weeks, sought to "change hearts and minds," while emphasizing to the audience at the start of his speech that the GOP presidential nominee has yet to be decided despite the seeming inevitability of former Massachusetts Gov. Mitt Romney's victory.
"We've been written off many times before. It may turn out we win the state of Iowa," he said. "We don't know what will come out next week with our primary, in August or in November, but we do know what is happening in our country, and we do know an idea whose time has come cannot be stopped by the army or politicians."
Sunday's rally suggested Paul was attempting to broaden his support beyond college campuses, where he reliably draws large and enthusiastic crowds. About 3,000 people gathered on the Capitol grounds, a group noticeably more varied in age than the one that gathered to hear the congressman last month on the University of Texas at Austin campus.
UT student Travis McCormick said Ron Paul's message transcends age barriers. "What people young and old like about him is he's a man of integrity," he said.
In addition to his presidential campaign, Paul discussed his opposition to presidential executive orders, the Transportation Security Administration, the Iraq war, the Obama administration, federal monetary policy and his belief in personal liberties.
Paul also sought to build momentum for Cruz, the former Texas solicitor general who is pitted in the Texas Republican Senate primary election against Lt. Gov. David Dewhurst, former Dallas Mayor Tom Leppert and former ESPN analyst Craig James.
Cruz lambasted the direction of the Republican Party in the last decade.
"The best thing to happen to the Republican Party was to get its teeth kicked in in 2008," Cruz said.
He also swung at Dewhurst for what he said was the lawmaker's failure to stand up to TSA when legislators last year tried to pass a bill prohibiting intrusive airport pat-downs. Cruz said that if elected he would support eliminating the U.S. Departments of Education and Energy, the National Endowment for the Arts and the IRS.
Cruz said his campaign was based on grassroots support from young people, Republican women and the Tea Party, not establishment Republicans. He said his own campaign message was consistent with the Pauls', and called them "clarion voices for liberty."
