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PITTSBURGH - Mitt Romney's campaign always makes his arrivals in various cities known to the local media, and in turn the public, but never before has a crowd of this size shown up to greet him. Upon landing here in Pittsburgh, Romney's aides appeared shock as they crowded around the windows to check out the crowd.

And Romney was visibly moved at the site of the crowd, hundreds of supporters crammed into a parking structure just outside the airport.

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Romney deplaned and walked toward a fence that separated him from the crowd, packed onto two levels of the garage.

He waved to the group with his left hand and placed his right hand over his heart for several minutes as they cheered.

Asked by ABC News how it felt to receive such a welcome, Romney turned and responded, "That's when you know you're gonna win."

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