The campaign that seems to have lasted forever enters its homestretch. Tonight marks the first of three presidential debates (8 p.m., ABC, CBS, NBC, PBS, Univision, CNN, C-SPAN, CNBC, Fox News, MSNBC) between President Barack Obama and Republican challenger Mitt Romney. For the record, the first Republican primary debate of the 2012 election took place on May 5. Of 2011!

Tonight’s event, at the University of Denver, will be moderated by veteran PBS newsman Jim Lehrer and will focus on domestic affairs.

The debate offers Romney a chance to introduce — or, reintroduce — himself to voters who have yet to focus on the race or make up their minds. Over the years, debates have provided challengers the opportunity to appear “presidential” and more up to the job than the incumbent. Or at least more likable. That was the case in 1976, when President Gerald Ford stumbled on issues of foreign policy, giving Democratic challenger Jimmy Carter an opening. Four years later, Carter seemed ill at ease compared to a confident Ronald Reagan, who assured voters that he was more than a genial Hollywood star. Romney’s supporters find the 1980 analogy apt because, just like Reagan, he is facing a president beset with a bad economy.

Glancing back at the year of the Carter-Reagan election, you can now see that even the prime-time television zeitgeist was moving in Reagan’s direction and beginning to tout his pro-prosperity mantra.

For years, television programs had celebrated the everyman. From Ralph Kramden to Archie Bunker, the average guy was king. The middle class was depicted as a kind of paradise. Even an all-powerful sorceress like Samantha Stephens on “Bewitched” wanted to join. The rich, when they were depicted at all, were pitiable, effete and detached, like the Howells on “Gilligan’s Island.”

Tonight’s other highlights

• Miami boot camp begins for a lucky few on “The X Factor” (7 p.m., Fox).

• The newcomers head to the mall with their alien friends on “The Neighbors” (7:30 p.m., ABC).

• Dean returns from purgatory on the season premiere of “Supernatural” (8 p.m., CW).

• “Life After Top Chef” (9 p.m., Bravo) debuts.

• “Food Paradise” (10 p.m., Travel) celebrates bacon.