Quick: Name the top 3 moments in vice presidential debate history.

Unless you were born after 1990 -- shakes fist at millennials -- the one that immediately comes to mind is Lloyd Bentsen's smackdown of Dan Quayle in the 1988 vice presidential debate.

If you were born after 1990, the one vice presidential debate moment that you can probably remember is "Can I call you, Joe" via one Sarah Palin.

Exactly.

As my colleague/archenemy Philip Bump has noted in this space earlier this afternoon, past polling suggests that no matter how well or poorly the vice presidential candidates do in this quadrennial debate it doesn't change the overall trajectory of the race.  Not a whit.

Think about it this way. When a highly sought-after recruit is considering where to go to college, do they make a decision based on how much or little they liked the assistant coach? No, of course they don't. The decision is based on what they believe to be their relationship with the head coach.  Now, if they like the assistant coach or the assistant coach speaks highly of the head coach, that can affect the recruit's overall perspective on the head coach or the program. But no one -- or at least no one smart -- is making decisions about their future based on the second-in-command.

That phenomenon is made even more acute by the nature of this presidential race.  Hillary Clinton and Donald Trump are worldwide celebrities about whom almost no one lacks an opinion. They are both larger-than-life figures who stand astride their two parties, blocking out any sunlight for other politicians.

And then there is the fact that both Tim Kaine and Mike Pence were chosen primarily for their steadiness and long records in elected office. The trait that recommended them both to their respective nominees was their solidness.  Neither Kaine nor Trump will cause any harm to a ticket. Which is good if you are running for president, but less entertaining or interesting if you are watching the debate/deciding who to vote for.

Yes, some of the coverage in the run-up to and aftermath of tonight's debate will suggest It Changed Everything. But, it almost certainly won't.  The best a vice presidential candidate can do in the VP debate is improve his or her own prospects for a future presidential run while smoothing out some of the hard edges of the party's presidential nominee. That's about it.