Via Nate Silver:
Only two surveys, one by ABC News and The Washington Post and one byRasmussen Reports, have tested Mr. Rubio’s popularity since the Senate reached the final stages of passing a comprehensive immigration reform bill. Both measured double-digit drops in his net favorability rating among Republicans.
Mr. Rubio is still very popular among Republicans, just not as popular as he once was, particularly in the days after the 2012 presidential election when he became a leading Republican voice and began being discussed as a top contender in the 2016 presidential race.
Indeed, Mr. Rubio led in an average of the first few 2016 Republican primary polls released after the 2012 election, but support for him has faded in more recent 2016 primary surveys.
In the four national surveys conducted in January, an average of 20 percent of Republicans said they would support Mr. Rubio for the party’s nomination in 2016. That number dropped to an average of 11 percent in the four primary polls conducted in June.