[American Constitutionalist]

" When the subject of politics inevitably came up, they all sat and quietly listened to me expound upon my conservative views, without interruption. In times past, they would have all ganged up on me, and shouted me down, but something had dramatically changed with them. "

Perhaps maybe they have crossed that line of " seeing the light " or perhaps they are on that threshold.
They need a soft gentle coaxing in the right direction.

In your case I would not try to rub it in if Obama loses.
It seems there is a very good opening for you there and if you had enough time you could be persuasive to have them actually vote for Romney.
My mom ?
She is or was a life long diehard FDR always voted Democrat.
Not so in 2008 and not so this year either, so there is hope.
In your case ?
Show them you love them, show them it's ok to let go of things that you thought were once true.

They could be looking for a reason to admit they were wrong ( not that you need them to actually admit it to you ).

Begin with a soft handed approach with them.
I am very sure that they are very aware of how they treated you, mocked you, ganged up on you in the past... but, show them grace.

[Kickass Conservative]

I voted for Perot in 1992 when I wasn’t really paying attention to Politics. Everyone sins...

I simply think this way now. If they Voted for Obama in 2008, it was probably due to Ignorance.

If they Vote for Obama in 2012, Ignorance is no excuse.

[Windflier]

I would not try to rub it in if Obama loses.

I wouldn't think of it, even though they rubbed my nose in their win, four years ago. It's just not how we conservatives roll.

I'm also not going to try to educate them any further. Been there - done that - have the scars to show for it.