Many pundits dismiss Thursday night’s Republican presidential debate as a non-event that changed nothing in the GOP race.

But what the faceoff in Miami did reveal is what could have been.

If the GOP campaign had started with four or five or six candidates – not an unmanageable field of 17 where the loudest, most obnoxious contender (Donald Trump) dominated the show – we would have a contest similar in tone to last night’s debate.

This was a quiet event focused on substance and policy, not the juvenile antics and name-calling of past debates.

It was an event which demonstrated that a mild-mannered Donald Trump, minus the attention-grabbing tactics, is far from impressive.

It was an event that showed what could have been for the Marco Rubio candidacy.

With his back against the wall, the Florida senator returned to his upbeat message of last fall. Hhe was articulate and poised, demonstrating how effective he can be on stage when he comes across as confident and knowledgeable. As Chris Cillizza of The Washington Post noted, Rubio’s solid debate performance demonstrated how he could have been a serious challenger to Trump and Ted Cruz — except for two big campaign mistakes.

One was the senator’s bizarre, robotic rhetoric at the debate just prior to the New Hampshire primary. The other was his decision, which he now admits was an embarrassing blunder, to launch personal attacks on Trump in a down-and-dirty fashion in recent weeks.

As for Trump, it was obvious that the campaign’s strategy for the night was: Don’t Let Trump be Trump. Many who watched the frontrunner’s staid performance on TV probably grumbled about how Trump was boring, that he wasn’t his usual entertaining self.  But what we saw was that if the celebrity businessman tones down the bloviating and tries to act presidential, he’s really not much of a factor.

What has been widely underreported is how many times Trump’s remarks were greeted with near silence, or just a smattering of applause or some hoots and hollers that seemed to be coming from a group 10 or 12 people. This was undoubtedly a hometown crowd cheering for Rubio, but it seemed fairly obvious that the moments when the audience felt that a candidate response had fallen flat belonged almost exclusively to Trump.

Too often, Trump has been allowed to wing it, answering questions with a string of superlatives without offering any policy smarts. On Thursday night, he seemed clueless about Cuban-American issues. He contributed virtually nothing to the discussion about Social Security’s long-term financial problems.

As Rubio said, Trump’s “numbers don’t add up.” But as long as Trump’s numbers in the delegate count look good, he will continue to get a pass for dodging specifics on policies and issues.