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The final debate in the closely-watched Texas GOP runoff election for a U.S. Senate seat turned into a contest to see which of the two rivals was most fiscally conservative and pro-free market.

The Tea Party-backed Ted Cruz, a Cuban-American attorney, tried to chip away on Tuesday at Texas Lt. Gov. David Dewhurst’s conservative credentials, painting him as an advocate of Medicaid expansion, soft on illegal immigration and saying he supported a state payroll tax while serving in the Texas Senate.

An often visibly flustered Dewhurst found himself on the defensive for much of the debate, shaking his head as Cruz lobbed attacks and halting as he defended his conservative record in the Texas Senate.

The two candidates fundamentally agree on an array of issues.

They both oppose the Affordable Care Act, which they refer to derisively as “Obamacare.” They both say they want to reign in spending and cut taxes. And they both prioritize efforts to secure the U.S.-Mexico border over addressing the problems faced by the estimated 11 million undocumented immigrants in the United States.

But Cruz, who is 41 and has never held elected office, staked out more extreme positions than the 66-year-old Dewhurst, a career politician who has presided over the Texas Senate as Lieutenant Governor since 2003.

“My touchstone for every question is the Constitution,” Cruz said, adopting the refrain commonly heard from Tea Party supporters.

When asked how he would provide health services for the estimated 1.5 million uninsured without expanding Medicaid or raising taxes, Dewhurst said he supported incentivizing doctors to adopt best practices to reduce wasteful spending and improve patient outcomes.

Cruz, by contrast, dismissed the idea that the government should provide health care at all.

“I don’t think it’s government’s job to find health care for people,” Cruz said. “I think it’s the individual’s job to find health care.”

Cruz went on the offensive against Dewhurst on illegal immigration—a key issue in the state that shares the longest stretch of U.S.-Mexico border—calling attention to Dewhurst’s 2007 support of a guest worker program for the state’s undocumented immigrants, announced at a speech in South Texas.

Cruz called the guest worker idea more expansive than President Obama’s decision to call off deportations for immigrants without criminal records who came here illegally as children—a policy that Cruz opposes and called “illegal.”

Dewhurst, who has taken a more pragmatic approach to the issue of illegal immigration, avoided clarifying whether he currently supports such a program.

Cruz also distinguished himself from Dewhurst with his full-throated support for a border wall estimated by the Department of Homeland Security to cost $7.3 billion, or $6.5 million per mile.

Cruz defended the border wall proposal even if it meant expropriating private property—a position that the debate’s moderators, WFAA reporter Brad Watson and Gromer Jeffers of the Dallas Morning News, said contrasted with Cruz’s message of fiscal conservatism.

“One of the specific powers and responsibilities of the federal government is to secure the borders,” Cruz said. “Property can be taken with due process of law and just compensation.”

Dewhurst said “a fence is absolutely warranted in certain places,” but argued that extending a wall across the length of the border was futile because “people go around walls and over fences.”

Cruz also hammered away Dewhurst for his support of a payroll tax—a position Dewhurst denies taking.

Politifact, a nonpartisan fact-checking organization, points out that Dewhurst opposed payroll taxes for most of his career but did in fact support an unsuccessful payroll tax proposal in 2005, acknowledged in a press release from his office at the time.

Admitting he lacked eloquence compared to Cruz, an attorney who argued and won several cases before the Supreme Court when he served as Texas Solicitor General, Dewhurst framed his business and military experience as assets Cruz doesn’t share.

“There’s a difference between being a debater and a fighter,” Dewhurst said. “I’ve been a fighter. I’ve built up a business from scratch.”

Cruz forced Dewhurst into a runoff for the GOP Senate seat ticket in a May 29 election, where he came in second with 34 percent of the vote. Though unable to seal the election, Dewhurst commanded a decisive lead then, coming in first with 45 percent.

But Dewhurst’s lead has continuously narrowed in a fierce campaign for the July 31 runoff election that has caught national attention. The race is now neck and neck, with polling data showing contradictory results.

A poll commissioned by the Cruz campaign from Wenzel Strategies released July 12 placed Cruz ahead of Dewhurst 47 percent to 38 percent. But a poll released the day before by the Dewhurst camp put him ahead of Cruz 50 percent to 42 percent.

Spending by national groups in the race is “extraordinarily high, with quite a few high-profile groups involved,” according to Viveca Novak of the Center for Responsive Politics, which tracks campaign donations.

The pro-free market Club for Growth, the largest single contributor to the Texas U.S. Senate race, has dropped over $4 million to support Cruz, according to data compiled by the CRP.  

Cruz has also picked up a larger share of out-of-state contributors and small donations than Dewhurst, with 25 percent of his donations coming from contributors outside Texas, compared to 5 percent of Dewhurst’s.

The broad national support Cruz has attracted owes in part to his high-profile Tea Party endorsements and brazen anti-establishment message.

“I am perfectly happy to compromise whether it’s with Democrats or anybody else,” Cruz said at Tuesday’s debate. “As long as we’re reducing the size of government.”

But Cruz has also ruffled feathers within his own party.

Cruz’s television ads blasting Dewhurst for supporting a payroll tax and failing to pass a bill that would outlaw “sanctuary cities” where undocumented immigrants face weaker enforcement riled the Texas GOP, prompting Republicans in the Texas Senate to publish an open letter defending Dewhurst’s record.

The letter, which does not mention Cruz by name but is clearly directed at him, was signed by all state GOP senators but one—Tea Party-backed Brian Birdwell.

As a Cuban-American with Tea Party backing, Cruz has drawn comparisons to Florida Senator Marco Rubio. But while Cruz has emphasized his father’s up-by-the-boostraps immigrant success story, he has not spent much time targeting Latino voters.

“Latinos are a relatively small share of the GOP primary electorate, somewhere between 5 and 10 percent,” Mark Jones, a political scientist at Rice University, told Fox News Latino. “For the Hispanics that are going to vote for him, he doesn’t need to make an appeal to them as a fellow Hispanic. But if he does anything explicit, that risks having a detrimental effect on some of his conservative base.”

The winner of the July 31 primary runoff will almost certainly walk away with the Senate seat, given that Republicans outnumber Democrats by a large margin in statewide races.