Donald Trump and Hillary Clinton have already started prepping for their three nationally-televised presidential debates, the first to be held at Hofstra University on September 26.    But will the debates really matter as much as so many analysts seem to predict?

Not according to most political scientists.  The dominant view among the “experts” is that most voters have already made up their minds about the candidates by the time the debates occur, typically late in the campaign season when opinions about them and the issues have already crystallized.

What does the research show?  A number of detailed academic studies have found that voter preferences toward the candidates moved barely at all between the pre- and post-debate periods.   Nate Silver, who’s made a name for himself predicting the outcomes of elections, noted a slight percentage shift in a number of debates that he studied — but not enough to alter the final outcome.

One methodological problem is how to separate out the effects of the debates from other developments or issues in the race that might overshadow them  In addition, some analysts have suggested that it’s not so much the substance of the debates – but the way the media spins the outcome that is the determining factor.

A case commonly cited is the 2000 debate contest between Al Gore and George W. Bush.  Most analysts found that Gore won on points, but after the debates, media commentators “spun” them as a victory for Bush.  And in fact, there was a strong shift in the pre- and post-debate polling from Gore up slightly to Bush ahead by 8 points.

Sometimes media outlets take completely contrasting views of what occurred in the debates.   And research shows that audiences often endorse what they hear from debate experts — to a shockingly large degree.

Another factor is the effect of the physical appearance and demeanor of the debate participants.  The case of John F. Kennedy vs. Richard Nixon – the first ever live televised presidential debate — is widely cited.  Those who heard the debate on radio gave Nixon a slight edge, but the television audience favored the tall, handsome and self-confident Kennedy over Nixon, who was sweating and appeared to be shifting nervously throughout the proceedings.

The three debates between Barack Obama and John McCain in 2008 may have exhibited a similar phenomenon.   Obama’s youthful telegenic looks gave him a favorable visual appearance while the camera seemed to magnify McCain age and sallow skin.  In a race where McCain’s age was already an issue, his appearance on television seemed to weaken him.  But few believe that Obama’s dominance — he won all three debates — derived from his appearance alone.

One issue analysts haven’t seemed to consider is that the challengers in the election tend to gain a greater advantage from debates.  Kennedy, Bush and Obama were all trying to bring their party back to the White House after two terms of rule by the other party.

It could be that the sheer appearance of challengers on the same debate stage in a position of parity with the “establishment” candidate tends to increase their stature as well as their visibility.

Debates also have the potential to magnify gaffes and missteps.   In 1992, George H.W. Bush impatiently looked at his watch several times during his debate with Bill Clinton, which seemed to reinforce the idea that he preferred to remain aloof at a time when the nation’s economy was tanking.

Another example was Gerald Ford’s muffing of a basic question regarding the Soviet Union and Eastern Europe in his debate with Jimmy Carter in 1976.   Pundits seized upon the gaffe, but despite a slight uptick in the debate’s immediate aftermath, Carter’s poll ratings actually began sinking thereafter.

All of which brings us to 2016.  Trump, arguably the challenger, should have a slight advantage going in because the bar for his performance is set so low.  Were he to hold his own against Clinton, and remain “presidential” in his demeanor, it might well increase his standing, especially with undecided voters

On the other hand, Trump is not a skilled debater, is often over-bearing, and lacks Clinton’s command of intricate policy details.  But so did Ronald Reagan in his debate with Carter in 198o.  With his trademark smile and deft comedic timing, he skillfully used it to his advantage.

Rest assured, in today’s increasingly polarized “Fox vs. MSNBC” media climate, Clinton and Trump are almost certain to “win” their first debate — with those that are already predisposed to support them, that is.

But after the first grand spectacle on September 26, the rest of us may soon be watching football.