As an indication of how bad last night's debate was for Trump, his supporters are going around on the Internet today saying "Debates don't matter, voters do!" This is, for reference, the exact same thing Rubio supporters said the day after his disastrous debate in New Hampshire, and we see how that turned out.
Look, it's entirely possible that literally nothing can dent Trump's support, but what we do know is that nothing like what happened to Trump last night has ever been tried. Marco Rubio, of all people, actually out-insulted Trump, but did so without stooping to Trump's rhetorical level. Whenever Trump has been attacked in previous debates, his comebacks have always lacked substance, but last night they in addition looked... lame.
For instance, when Rubio busted Trump's chops by saying, "Gosh, Donald, it sounds like you're repeating yourself," Trump responded "I saw you repeat yourself five times in that debate a couple weeks ago!" Hey Donald, thanks for demonstrating that you got the joke about 10 seconds after the rest of America. Second, Rubio actually got the last word in during this (and several other exchanges) by saying, with his biggest grin, "I saw you repeat yourself five times five seconds ago!" Trump could only stare in dumbfounded silence.
Jeb Bush has attempted this trick in previous debates, but last night showed why Marco Rubio is still in this race, and Jeb Bush is not. Rubio did to Trump what Christie did to Rubio. Trump's sad and pathetic rejoinder was that Rubio lost to Christie a couple weeks ago.
In every single debate, Trump has looked ill-informed and boorish. That hasn't hurt him at all to this point. Last night, for the first time, he was made to look beta. Low energy, if you will. And it looked as easy for Rubio as taking candy from a baby. And Trump's sullen, befuddled silence likewise opened him up to several devastating salvos from Ted Cruz, who was able for the first time to effectively drive home the point that Trump is a liberal, in addition to being an ill-informed flip-flopper.
That having been said, even if Trump's numbers don't fall, last night demonstrated that Trump can be beaten. It likely kept the cap on Trump in the 30-35% range and bought both Rubio and Cruz some breathing room.
Most importantly, it helped the supporters of both Cruz and Rubio feel better about the other guy's chances to take on Trump. I know firsthand after my post yesterday that the partisans of Cruz did not believe that Rubio had what it took to take on Trump head on before last night, and the Rubio partisans felt the same about Cruz. Just based on the Twitter reactions from prominent partisans of both candidates, a strange new respect dawned for the other guy that had been absent for too long.
Although the moderators tried to play "let's you and him fight" between Cruz and Rubio all night long, both candidates wisely refused to take the bait, and instead continued their relentless tag team on Trump. If that dynamic continues, this race might well have changed permanently, and not in Trump's favor.