Even though Christie tried to defund Planned Parenthood five times in New Jersey, he was always viewed as a moderate and unreliable Republican who cozied up with President Obama when it was convenient. Christie would have been a harder sell to evangelicals and hard-line Republicans.
Pence also brings Midwestern values to the ticket and, as governor of a must-win state, he has a pre-built network of support — at least in theory. Trump and Christie would have been too reliant on the Northeast. Sure, Gingrich represented Georgia, but he is viewed as a Washington insider and his fiery appearances on Fox News only reinforce that image.
It also would have been much more difficult for Gingrich to attack the presumed Democratic nominee Hillary Clinton as an insider when he was Speaker of the House during her husband's administration.
Trump needs a "yes" man — a VP who will take direction well and not question authority. Both Christie and Gingrich might have publicly supported Trump but their loyalty was never guaranteed.
Christie knows deep inside that he owes nothing to anyone. As governor of New Jersey, he talked down to teachers, scolded the press, belittled unions and used his bully pulpit as a sword. Christie proved he was a strong street fighter, and that would have been another risk for Trump if the polls started going down.
Plus, Gingrich knows the game of politics better than anyone. He used his political acumen to navigate to the top of the House. This could work to Trump's advantage, but likewise, it could flip against him just as easily. It doesn't help that Gingrich is also an insider in the year of the outsider.
But one of the biggest advantages that Pence brings to the ticket is his ability to adapt and brand himself into what Trump wants and needs.
Christie and Gingrich are already molded. You can't rebrand them with the public, like you can with Pence who is unknown to the American voter. That means, if done correctly, Trump can bend Pence into the candidate that best serves his needs.
It's a conventional and safe pick that just might bring over those undecided voters who are afraid of the unconventional Trump style.