Nitpick: Only 43 people have been president.
Hardly anything the President does is mandated. Most of the things a President does all day long are not mandated, but everybody expects the President to do them. They’re part of his job as the job has come to be defined de facto over the past 200+ years.
And so is running for re-election. You probably don’t remember when Johnson decided not to run, but that rocked the country. And he wasn’t even a true one-term president since he served part of the previous president’s term. So did the last president before him not to seek re-election, Calvin Coolidge. You have to go back to the 19th century and a different political world to find a true one-term president by choice.
The president is leader of the party and is responsible for ensuring the party’s continuity and success. Not running for re-election would be fatal. Of course it’s part of his job, just as it’s Mitch McConnell’s job to say that his job is to make Obama a one-term president. Saying anything else is folly.
Yeah, yeah, Cleveland counts twice.
All I know is I’m bummed. 
I was really looking forward to at least a few Bachmann or Cain or Gingrich VS Obama debates…with Romney, it will still be an easy win for Obama but hardly the bloodbath I was hoping for.
Oh well.
Depending on the political leanings of whatever 3rd party candidates emerge, I expect more “Republican” debates, between the GOP candidate and one or more conservative independent candidates (I don’t see a left independent candidate popping up). At a minimum, I don’t think Mitt Romney (assuming he gets the nod) has seen the last of Ron Paul.
Has any other majority leader said his job was to make the sitting President a one-termer? Was McConnell the only one doing his job?
The President works for us, not for his party, whichever it may be. He’s the President of the United States, not the President of the X Party.