Ted Cruz ratcheted up his rhetoric against rival Marco Rubio Sunday, claiming a vote for Rubio is tantamount to support for amnesty for undocumented immigrants.
"A vote for Marco is a vote for amnesty," Cruz said.
"The fact that on a signature issue, Marco Rubio broke his promise to the American people, is significant," Cruz said.
"The central issue in this primary is trust," Cruz said on CNN's "State of the Union."
Rubio has leveled similar criticism againt Cruz, accusing the Texan of distorting his own prior support on immigration reform.
Rubio and Cruz are Senate colleagues, who entered the chamber in 2011 and 2013 respectively.
"When we got to Washington, he and I made very different decisions. He decided to break the promise to the people who elected him," Cruz said. "Not only did he not lead the fight against amnesty, he led the fight to pass amnesty."
The immigration reform proposal Rubio backed, according to Cruz, "granted amnesty to twelve million here illegally."
The bill, sponsored by a bipartisan group of senators and passed by the Senate in 2014, gave undocumented immigrants in the United States a so-called "path to citizenship" if they met various conditions. It also would have sharply increased spending on border security.
Republicans who supported the plan argued the GOP cannot afford to alienate the growing block of Hispanic voters by opposing any plan that grants any sort of clemency to the millions of undocumented immigrants in the country.
"If we nominate someone who has the same position on amnesty as Hillary Clinton, we will lose," Cruz said.