The Service Employees International Union is out blasting four Republicans in tough races on immigration reform, seeking to drive up Hispanic turnout against them.

The SEIU is out with new Spanish-language radio ads targeting Reps. Cory GardnerCory GardnerRepeal of Obama drilling rule stalls in the Senate Colorado Dem at the center of Gorsuch confirmation fight Gorsuch sails on day one, but real test is Tuesday MORE (R-Colo.), Mike Coffman (R-Colo.), Joe Heck (R-Nev.) and David Valadao (R-Calif.).

Gardner is a top Senate recruit in a state with a large Hispanic population, while the other three are top Democratic targets in Latino-heavy swing districts.

The ads hit the four on immigration reform, tying them to the national party.

"It's simply unacceptable: Mike Coffman and Cory Gardner, together with the Republicans, have blocked immigration reform. Worse yet, they voted to deport our DREAMers. And now, this is the limit — Republicans attack our children at the border as if they were criminals," the ad says in Spanish.

"One Republican Congresswoman even said that immigrants are invading the United States and suggested many recent immigrants could be rapists and murderers," the ad continues, referring to Rep. Michele BachmannMichele Bachmann'Real Housewives' producer 'begging' Conway to join cast Ex-rep admires furs amid PETA inaugural gala Why Republicans took aim at an ethics watchdog MORE (R-Minn.).

The ads spotlight how liberal groups are seeking to nationalize the immigration battle for electoral gain. But it could be tougher in some of these districts than others — Valadao, for instance, has embraced immigration reform.