U.S. Republican presidential candidate Sen. Ted Cruz, who used to heap praise on businessman Donald Trump, now says that the real estate mogul’s immigration plan amounts to amnesty for undocumented immigrants. Cruz’s statement is the latest jab between the two candidates who are neck-and-neck in Iowa polling.

Trump, who ascended quickly to the top of national polling after he announced his candidacy and called Mexicans criminals and rapists, favors a roundabout method of granting amnesty, Cruz said during an interview with ABC Friday. The Texas senator added Trump wants to deport undocumented immigrants living in the United States and then let them back into the country as U.S. citizens. "Basically you make them fly back to their country for a minute, touch the ground, and then they come back with amnesty as citizens," he said.

He also attacked Trump for his past positions on immigration reform.

“I would note at that time, right in the middle of the fight, Donald Trump was publicly supporting amnesty. He was supporting [Sen.] Marco Rubio's Dream Act," Cruz said, referencing another presidential candidate who worked on comprehensive immigration reform in 2012. "He was criticizing Mitt Romney for being too tough on immigration. That's where Donald Trump was in 2013. Now, when he launched his campaign for president, suddenly he discovered illegal immigration was a problem."

Cruz is hoping to capitalize on his recent rise to prominence in polls. The Real Clear Politics average of polls indicates Cruz is down 2.6 percent at 26.4 percent of the vote compared to Trump’s 29 percent. That’s a bit of a drop from earlier this month when Cruz was beating Trump by about 4 points.

Cruz has made headway in national averages of polls as well, though not nearly as successfully. He is currently trailing Trump by 16 points in polls and is in second place with 18.8 percent of the vote. That’s a substantial jump from November, when he polled in fourth place nationally.