Lieberman actually, despite the hate he receives from leftists here. He nearly helped Gore win Florida.
Bob Graham, who at that point won statewide in Florida 5 times (IIRC at least) would've helped Gore in Florida far more than Chancellor Palpatine, if he even helped at all.
To answer the question of the thread it was Pence. Given how close the election was, Pence's appeal to evangelicals, many of whom at the time were reluctant to get behind Trump, might've very well made the difference. Gingrich or Christie, Trump's runner up choices, most certainly would've lost the GOP the election, Gingrich in particular.