Because Rubio has taken strong, articulate positions on pro-life and religious liberty issues, the very issues that matter deeply to the social conservatives there at the Values Voters Summit today, issues on which Rubio has a much stronger history than Trump. Rubio is also very strong and articulate on foreign policy. Yes, believe it or not, there are some issues conservatives care about other than immigration. Also, some of the people there today may not appreciate Trump's penchant for arrogance and cheap insults. They may find it unbecoming for a presidential candidate.
Well then, all Rubio has to do is convince his followers that he is no longer an amnesty-loving mini-Jeb, and then get his polling numbers up into Trump territory.
I love how you overlook the “cheap” insults that are hurled at Trump first. It must be sad to be so blinded. I watched the feed from OK, and when Trump mentioned certain things - the crowd booed - not at him but at the subject matter. That’s exactly what happened today with Rubio too - whether you want to admit it or not. I guess you are an amnesty lover - which is an enemy to this country. Just because Rubio can cite facts and figures, doesn’t make him strong on anything. He misses a lot of votes in the Senate. Yeah, he’s articulate because he has a smooth, glib tongue, which is all phony.