Sen. John Cornyn, R-Texas, left, and Democratic challenger David Alameel greet each other at the start of their debate at Mountain View College campus in Dallas tonight. (AP Photo/Tony Gutierrez)

WASHINGTON – Sen. John Cornyn portrayed himself Friday night as an agent of change in Washington, as rival David Alameel blasted him for blocking immigration reforms while kowtowing to Wall Street.

This was the first and only debate of the contest, as Cornyn seeks a third term and Alameel claws for traction.

With Univision as the debate host, a hefty chunk of the questioning was aimed at immigration policy – an area of especially clear disagreement.

Cornyn, who has long resisted legalization for the 11 million people in the country illegally, called himself a “strong supporter of immigration reform.”  He agreed that young people brought to the country illegally by their parents – the so-called “Dreamers” – should be eligible for college aid.

But he called it politically impossible to pass a so-called “comprehensive” overhaul, and argued for taking smaller steps with broader support.

“I wouldn’t hold my breath for Republicans to offer you any immigration reform,” Alameel said.

The vast majority of immigrants have been in this country for years, breaking no laws and working hard. They “deserve a path to citizenship,” he said.

Cornyn proposed a flexible cap on immigrant visas, fluctuating with the U.S. economy and needs of employers.

“Of course we need to increase quotas” Alameel shot back, adding that this sidestepped the core issue, citizenship. Without that, he said, “It will take us a hundred years to give the relief that our Latino community deserves.”

The debate, at Mountain View College in Dallas, offered Alameel a rare shot at making headway against an incumbent with a huge edge in name identification and fund-raising. He labeled Cornyn a “do nothing senator. Our country burns while Cornyn fiddles.”

These and other barbs may not be seen widely enough to make much difference. The Dallas Univision station and Texas Tribune streamed the debate live online. Univision viewers can watch the debate in Spanish on Saturday night. C-Span will broadcast it Wednesday night in English.

Cornyn, the No. 2 GOP leader in the Senate, portrayed Alameel as a potential reinforcement for Democrats in the final two years of the Obama administration.

“What we need is new leadership and a new direction. We don’t need people who will go to Washington and support the status quo—the obstruction of the majority leader and the policies of the president,” Cornyn said.

Alameel asserted that Wall Street interests control the Republican Party and “John Cornyn is one of the leaders of that establishment, who only care about themselves….He’s turning our country into a minimum wage nation and we say enough is enough.”

They disagreed on a host of issues.

Cornyn called it “dangerous” to make marijuana legal, even for medical purposes. Alameel argued for full decriminalization. “Having prohibition didn’t work,” he said.

Cornyn reiterated his dim view of the Affordable Care Act. Alameel called Obamacare “a good step in the right direction” and argued that “Republicans have to stop saying no” and should work to improve it.

Both rivals called it a bad idea to make English the nation’s official language, though unlike Cornyn, Alameel said government documents should be offered in a variety of languages to ensure that people who haven’t learned English aren’t “abandoned.”

On the Ebola crisis, Alameel agreed with calls coming mostly from Republicans in Congress – and a few Democrats – for a travel ban on West Africa. “Yes,” he said, “we need to restrict flying. In any epidemic you have to restrict the flow in and out of that affected area.”

Both noted the lack of preparedness by Texas Health Presbyterian Hospital Dallas.

“There was no leadership from the White House and from the federal government,” Cornyn said.

Alameel also worries about lack of preparations.  ”If we have an epidemic, the first nine patients will be taken care of, and the other 100,000 will die,” he said.

Alameel was asked about the $15,000 or so he donated to Cornyn a decade ago.

“This is one terrible mistake I have to live with,” he said.

Cornyn wasn’t about to let his rival off the hook so easily. “He was an enthusiastic supporter of mine and Gov. Perry… and Republicans up and down the ticket.” he said.

On the president’s handling of the Islamic State terror group, Cornyn blasted the refusal to put American “boots on the ground.” Alameel lauded the president for bombing ISIS but warned that “we don’t need to create another big war.”

Social issues offered more bright lines.

Cornyn defended Texas’ tough law imposing requirements that forced most of the state’s abortion clinics to close. Alameel said that as a Catholic he doesn’t believe in abortion but wants them to be legal and available.

On same-sex marriage, Cornyn said that “I am pro-traditional marriage” and wants the federal government to respect Texas’ views that marriage should only be between a man and a woman.

Said Alameel, “We should move on from these divisive issues.”

Staff writer Michael Marks contribute to this report.