TROY, Mich. – If Hillary Rodham Clinton wants to restore her tattered reputation and repair the party she has shattered, there is only one place for her to be tonight: St. Paul, Minn.

That is where Barack Obama will kick off his general-election campaign tonight.

He chose the convention center in St. Paul because it is the very hall where Republicans will officially nominate John McCain later this summer.

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A surprise appearance and endorsement by Clinton – who is scheduled to hold her own event in Manhattan – would allow Democrats to mark that territory in history as the heart of a new and perfect unity for the party.

The election-night festivities would begin as usual with Obama mounting the stage before 20,000 wildly cheering voters.

He would start his victory speech and then pause. After a dramatic silence, he would say he wants to introduce a very, very special guest.

Already buzzing with giddiness, the puzzled crowd whispers and speculates.

The curtains spread, and to the tune of “I Will Survive,” a face unimaginable yet so familiar appears. Hillary Rodham Clinton, her granite smile, steady wave – even her cheery yellow pantsuit – would in an instant become so brave and honest and selfless.

She would endorse Obama in biblical terms and embrace him – literally – with both arms. Obama would bury her in the genuine gracious praise that comes so naturally from him.

And just when the drama could not possibly heighten, the curtains would part again and out would walk her husband and her daughter, along with Michelle Obama and their two girls.

In that instant, everyone would forget all there has been in this campaign to dislike about Bill and remember why they once loved him.

A warm family embrace would underscore just how much Hillary gave up to be there, in the name of something much bigger than herself.

It’s been a long and nasty fight, and Hillary has just one card left. But it’s an ace. Will she play it?

churt@nypost.com