The first of three high-stakes presidential debates is set for Monday, giving millions of voters who did not cast their ballots for either Republican Donald Trump or Democrat Hillary Clinton their closest look at the contest for the White House.

Expect the 90-minute showdown to be one of the most watched presidential debates ever, with an audience that analysts say could venture into Super Bowl-sized ratings by exceeding 100 million viewers.

The vast majority of voters usually have hardened their opinions by the time presidential debates take place. But in this year's lesser-of-two-evils battle, Monday's head-to-head matchup might play an outsized role.

Some 34% of registered voters said the set of three presidential debates that start on Monday in New York would be extremely or quite important to their decision. 

Among Republicans, 37% said the debates would be important to them, while 31% of Democrats said the same.

More: What to look for in the first presidential debate

More: Where to catch the debates in Georgia