As I watched Donald Trump “introduce” Mike Pence — and by that I mean talk about himself for 30 minutes — I just kept thinking: why did the Indiana governor agree to this?

After all, it is not possible that Pence did not know what he was getting into. By this point, Trump is a known commodity in GOP circles. You know what you are getting.

So, why then? Why put yourself so close to someone who has shown little regard for the party he will lead in a matter of days and even less regard for any politician not named “Donald Trump”?

Here’s what I came up with:

1, Pence wanted out of Indiana

Pence returned to his home state to run for governor in 2012 with a clear eye on it being a more effective launching pad for his national ambitions than a congressional seat — even one in which Pence was part of the GOP leadership.

But his return to Indiana did not exactly go according to plan — going home is never what you think it will be; just watch Beautiful Girls. Pence’s tough road became national news last year when he signed a religious freedom law that drew massive, negative attention. Pence quickly amended the law in hopes of salvaging something from the political wreckage and wound up succeeding only in making his social conservative base angry.

The result of all that craziness was a vulnerable Pence as he looked to his 2016 re-election race. Democrats had recruited former state House speaker John Gregg, a serious, credible and generally conservative candidate. Independent polling in the past few months showed that the race was surprisingly competitive.

So Pence got out while the getting was sort of good.

2, Pence was always more comfortable on the national stage

This from Indianapolis Star political columnist Matt Tully:

“Pence is a creature of Washington. That is where his closest allies and advisers are, and his skills as a talking-point communicator and as a partisan fighter fit well on Capitol Hill. They are not particularly beneficial in the more pragmatic role of governor.”

Sometimes what you think you want is a) not what you want and/or b) not what you’re best at. That seems to be the case with Pence as governor of Indiana. It is hard to argue that he prospered far more in his decade in the House — quickly rising up the leadership ranks and becoming “someone to watch” — than he has during his four years as governor. Signing on with Trump allows Pence access back to Washington and the national stage. And at a very, very high perch.

3, Pence has his eye on the future

No matter what you think of Trump and his chances of winning, it is hard to argue that “vice-presidential nominee” looks bad on Pence’s résumé.

If Trump loses, Pence can make the case to the real estate mogul’s supporters that he is the natural landing spot for them in 2020.

And he can make the case to the GOP establishment that he took on the vice-presidency slot for the good of the Republican Party — in hopes of modulating Trump and making him more electable. Would anyone blame Pence for failing in that endeavour? Hard to see how.

Assuming Pence runs a credible and respectable bid as vice-president — in other words, the anti-Sarah Palin approach — he has probably guaranteed himself a slot in or close to the top tier of 2020 Republican candidates.

On the other hand, let’s say Trump wins. Suddenly, Pence is vice-president — and first in line to be the Republican nominee in 2024 or 2028.

Either way, it’s a win-win for Pence.

4, He genuinely thinks he can help Trump to beat Clinton

I believe Pence when he says that one of the leading reasons he said “yes” to Trump was because he does not want Hillary Clinton to be president and is willing to do whatever it takes to keep that from happening.

Pence came into politics as a principled social conservative fighter and clearly disdains what he believes the Clintons — and the broader Democratic Party — stand for.

Pence has probably convinced himself that he can change Trump — or at least bend Trump to his will — enough that the two of them can take advantage of the distaste for Clinton in the country and actually win this thing. And that he may be the only person who can pull that feat off — never underestimate politicians’ ability to believe in their own uniqueness.

•Chris Cillizza writes “The Fix”, a politics blog for The Washington Post. He also covers the White House