SAN MARCOS, Texas — It's a battle on both sides of the political aisle.

For the Republicans, two constitutional conservatives vying for their party's nomination in the May 22nd runoff.

"There's a lot we need to do to reduce spending, to give us healthcare freedom back, to secure our border and create an immigration system that will work with the country, that will be America first,” said U.S. House District 21 candidate Chip Roy.

Former congressional aide Roy touts the backing from his former boss — Sen. Ted Cruz.

While his runoff opponent, Boerne businessman Matt McCall, is pledging to limit his years in office.

"I want to go for six years and fight for our values, fight for the interests of seat 21. It's a very rapidly growing area here along I-35 and I live in Kendall County,” Mcall said.

On the Democratic side — 20-year Army veteran Joseph Kopser believes his experience on the battlefield and private sector, makes him the best choice.

"When you marry the experience of the military and business, and you lay it on top of this district with the unbelievable opportunity for innovation and growth and business, to provide people the meaningful work the return on a day's work and the investment in their community," Kopser said.  

While opponent Mary Wilson describes herself as a progressive Democrat who believes in compassion.

"As an educator, as a minister, one of the things I look at is what is good for the people who are most in need. Not what is going to make the wealthiest people make the most money,” Wilson told Spectrum News.

All four bring their own ideas to the table when it comes to immigration.

"You need to seal the borders. I'm not against immigration, I'm for legal immigration,” said McCall.

"If we want to have legal immigration, let's rewrite the laws. But I am not up for traumatizing children and separating them from their parents,” added Wilson.

"Over a million people legally coming into our country every year -- let's make that system better, make it more efficient, more effective, there's lots of ways we can all agree to do that. But we have a duty to defend our border,” Roy said.

"This is where we are: A country that made a promise to DREAMERS, who through no fault of their own are here today, playing by the rules and now they want to change the rules. That's not right, that's not the American way of doing it,” Kopser mentioned.

The winner of each run-off will face each other in November.

District 21 spans northern San Antonio, the Hill Country, New Braunfels, and parts of Austin. The Republican candidates hoping to hold on to the longtime GOP-held seat of Lamar Smith, while the Democrats are banking on picking up some Republican voters that are disillusioned with President Trump and the direction of their party.