If you watched last night’s Republican presidential debate on CNN, you had to almost feel sorry for Donald Trump.

Almost.

And you have to wonder why Marco Rubio — the only Republican candidate who can beat Hillary Clinton, but running neck-and-neck with Ted Cruz for distant second in his party’s nomination race — didn’t take the kid gloves off sooner.

Rubio had Trump flummoxed, flustered, stammering and stuttering with constant jabs and one-liners during last night’s debate, which left the audience roaring its approval and Trump looking furious. And when Rubio paused to catch his breath, Cruz lit in. 

Last night’s debate proved why Trump will be a terrible nominee. He’s emerged unscathed from the debates up to this point because he’s sharing the stage with way too many candidates. But as the number has been whittled down, the debates have increasingly become mandates on Trump’s policy proposals, and he simply has no clue. His campaign has been built on insulting his opponents and shallow one-liners like “Making America great again,” but when his feet are held to the flames, Trump’s shallowness shows. Big time. He’s not a great debater and Hillary Clinton will destroy him in a one-on-one debate.

Of course, conservatives who are intent on voting for Trump don’t see this because they refuse to see it. Just take a look at the Drudge Report’s poll from last night’s debate. Fifty-six percent say Trump won the debate, more than 35% more than either Cruz or Rubio. Yet there’s no way any reasonable person could’ve watched the debate and come away with the impression that Trump won, or even close.

This exchange on healthcare summed it up perfectly. Rubio was able to use a self-deprecating approach to turn his biggest criticism — saying the same thing over and over — into an advantage that left Trump fuming but unable to respond.