Without a doubt Flake has the most pro-mass immigration record. He has a career C rating from NumbersUSA, but he has an F- on amnesty, chain migration, and increasing legal immigration. Flake sponsored or voted for amnesty six times. He has often taken the lead being the primary sponsor with Luis Gutierrez(D-IL) of the STRIVE Act in 2007. (The Strive Act would have granted amnesty to virtually every single illegal alien in the country. Additionally, it would have created a massive new guest worker-program that would allow 400,000-600,000 additional foreign workers and unlimited spouses and dependents to sign up for a six year visa during which time they could apply for permanent residency.) Flake opposed Arizona’s Proposition 200 and SB 1070, although he claimed to be against Obama’s subsequent lawsuit...Flake is already cognizant that this record will be a huge liability in the Republican primary, as evidenced by the fact that he voted against the DREAM Act. But as of yet, he has not been willing to do a complete McCain-style 180 on the issue.
Arizona Senate candidate flip-flops on immigration, by Catalina Camia, USA Today, Mar 23, 2011.)
And also to patriotism.