>> there was a battle over amnesty, and some chose, like senator rubio, to stand with barack obama and chuck schumer and support a massive amnesty plan. >> reporter: that's a reference to the 2013 immigration reform bill rubio helped draft. it ultimately failed, but the bill would have granted legal ioatus to the estimated 11 million undocumented immigrants in america. cruz said today that's the definition of amnesty. >> i oppose amnesty. i oppose citizenship. i oppose legalization. for illegal aliens. i always have. and i always will. >> he's not told the truth about his position in the past on legalization. >> reporter: rubio says cruz is forgetting the facts. cruz offered an amendment to that bill that would have provided green cards and work permits to undocumented immigrants, but deny the them citizenship. >> he said at the time, and he repeated to multiple media outlets for months, that he supported legalizing people who were here illegally. >> reporter: in the crucial early state of iowa, a recent