Trump is falling for a 'deplorable' trap

When you find a winning horse, you just ride it all the way to victory… right?

Someone should tell that to Donald Trump, who looks like he might be making a key error and choosing the wrong curtain in this latest round of "Presidential Election Let's Make a Deal!"

Behind curtain #1 we have Hillary Clinton's brutal "basketfull of deplorables" comment caught on tape during a fundraiser Friday night where Clinton literally said half of Trump's supporters were racists, sexists,homophobes, etc. The comment seemed eerily reminiscent of the video catching Mitt Romney's "47 percent" comments in 2012 that were deemed so harmful to his ultimately unsuccessful campaign.

Behind curtain #2 we have Clinton and her campaign's deceptive and cagey conduct during and after Clinton's medical episode on Sunday afternoon. Note that the key issue here is not just Clinton's health, but her honesty and transparency, or lack thereof.

Based on Trump's comments during his interview Monday with CNBC's Squawk Box and his big rally in Asheville, North Carolina that night, Trump is going with curtain #1 and looking to make as much as he can out of the "deplorables" comment. First on Squawk Box he took a very circumspect and reserved stance on Clinton's health, and didn't even mention her campaign's many-revised statements and clarifications about their candidate's condition. Then at the Asheville rally, Trump brought on the stage a diverse group of his supporters who all mockingly asked Clinton if they were what she meant by "deplorable."

Simply put, Trump is choosing the wrong curtain. And there are two big reasons why.

It's not that pushing back on Clinton's smearing of his supporters doesn't have some political advantages. But mostly it just fires up Trump's existing base of support, some of whom are now making and selling out t-shirts that proudly say things like "I'm Deplorable!" on them.

But conversely, it also fires up Clinton's supporters.

From New York Times editorial writers to her fans on social media, there are dozens of examples of Clinton backers who clearly agree with the characterization of Trump voters as dangerous hate mongers. And Trump's decision to focus on this basically asks undecided voters to consider just how many of his supporters are bigots, not if there are any bigots at all. Trump should simply drop this push back effort as a main focus of his campaign as soon as possible before it potentially backfires.

Before it's too late, Trump needs to shift to curtain #2 and focus not on Clinton's health, but how her medical episode Sunday provided yet another example of what even prominent liberals consider to be her problems with the truth. When Clinton's trustworthiness and honesty are the focus, things go much better for Trump. That's been true all year.

Trump's initial surge in the polls after he clinched the GOP nomination came when FBI Director James Comey reminded the entire country about Clinton's fuzziness with the truth connected to her private email server scandal. Even though Comey decided not to indict her, his much-watched announcement and detailing of Clinton's questionable behavior put the entire issue and her history of debunked denials connected to the scandal in the spotlight.

But as the weeks after Comey's annoncement passed, the voters seemed to forget about it and Clinton's poll numbers recovered. That recovery abruptly ended late last month when the transcript of Clinton's response to FBI investigators' questions about her emails were made public. The surprising number of hard-to-believe "I can't recall" responses and Clinton's other obfuscations surprised even some of her harshest critics, and her poll numbers started to sag again.

There's a simple reason for all of this, and it's not really about emails. The problem is the vast majority of the voters do not trust Hillary Clinton is telling them the truth at any given time. Poll after poll has told us this for more than a year. But this problem seems to really hurt her when something happens to remind the bulk of what's left of undecided voters of this fact.

Clinton's campaign has done just that several times with its multiple explanations, backtracking, and other smokescreens connected to her near-collapse at that 9/11 memorial ceremony Sunday. The lack of transparency connected to the incident has been blasted by several Democrats and members of the usually Clinton-friendly news media over the last 48 hours.

If they can find a way to attack Clinton's honesty while not gloating over her possible health problems, perhaps Trump can too. At the very least, he needs to find a way to keep reminding the public that it's never really trusted Clinton in the first place.

And the time to strike on that issue is now. The latest NBC News/SurveyMonkey Weekly Election Tracking Poll has Trump and Clinton virtually tied in unfavorable ratings at 60 percent and 59 percent, respectively. The same poll shows Clinton with just a two-point lead against Trump in the four-way race with Gary Johnson and Jill Stein.

That poll and many others show that independent voters will decide this election. So ask yourself, what will sway those voters more: an insulting comment from one candidate about the people who already back her opponent, or more evidence that one candidate is not ever comfortable with the truth? The answer should be obvious, but it's apparently not yet all that clear to the Trump campaign.

Commentary by Jake Novak, senior columnist. Follow him on Twitter @jakejakeny.

For more insight from CNBC contributors, follow @CNBCopinion on Twitter.