Marco Rubio doesn't just repeat talking points during debates; it seems he also does it while delivering his stump speech. Not just by delivering the same speech over and over again (everyone does that), but in this case by delivering the exact same sentence — about how it's hard to raise kids in the 21st century with churchy values because nefarious forces in pop culture want to ram other values down our throats — twice in a row.
Check it out:
At 00:10: "And we know how hard it's become to instill our values in our kids instead of the values they try to ram down our throats."
At 00:19: "It's become harder than ever to instill in your children the values they teach in our homes and in our church instead of the values that they try to ram down our throats in movies, in music, in popular culture."
Andrew Prokop swears he saw Rubio being incredibly impressive with his own two eyes at a New Hampshire town hall, and I've heard very positive things about Rubio from people who worked with him on the Gang of Eight immigration reform bill (of course, he may not want to talk about that these days). But there's certainly something odd lacking the situational awareness to remember when you just said something minutes or even seconds ago.
Part of what makes primaries interesting is that random gaffes that wouldn't matter at all in a general election can make a difference here. It's possible nobody will care about these technical glitches Rubio is experiencing, but the GOP primary features a reasonably crowded field of reasonably similar candidates. There's very little distinguishing Rubio from, say, Jeb Bush, except for the perception that Rubio is dynamic and charismatic whereas Bush is lame. Small stumbles can wreck that kind of perception and tip people over to another candidate in a way that wouldn't be possible if there were big ideological gaps.