By Michael D'Antonio and Peter Eisner

(CNN) -- Now familiar as a smiling, nodding presence at the President's side, Mike Pence was little known outside of his home state of Indiana when Donald Trump selected him as his running mate in 2016. A bit more than two years later, as he crisscrosses America to campaign for Republicans in the midterm elections, Pence is setting himself up to replace his boss if Trump leaves office early or does not seek re-election.

"Mike will be ready" is the line Pence's aides and allies use as they contemplate his place in a post-Trump world.

Pence would never admit this. He plays the part of unctuous toady so fully that the conservative writer George Will called him "America's most repulsive public figure." But don't be fooled. The vice president is doggedly pursuing his own ambitions on the side. The Oval Office has been his goal since high school. He has seeded the federal government with his loyalists and is building his own nationwide political organization.

He is acting, in fact, as if he is on a mission from God. Some may laugh, but many conservative Christians believe that God is merely using Trump to prepare the way for a so-called true man of faith. Pence's rise to power would affirm the "Cyrus prophecy," which became a popular notion among Christian right circles when Pence joined the 2016 ticket.

Cyrus was a Persian king whom the Old Testament credits with returning the Jews to Jerusalem. He was a pagan who nevertheless served God. Right-wing evangelists such as Lance Wallnau cited that tale in 2016 when they declared that Trump -- a profane and sinful man -- could nevertheless do God's work and was thus worthy of conservative Christian votes. An estimated 80% of white evangelicals gave Trump their votes.

The story of Cyrus resonates with many right-wing Christians because they imagine themselves to be persecuted like the Jews of old. Despite their vast wealth, power and numbers, these believers cite developments such as same-sex marriage and the use of ecumenical phrases such as "happy holidays," instead of Merry Christmas, as evidence they are a minority under siege. They imagine themselves to be victims of a culture war and feel that something must be done to defend an old order that they once dominated.

As a radio host, member of Congress and then governor of Indiana, Pence made himself the most successful conservative Christian politician of his generation. Indeed he says he is "a Christian, a conservative and a Republican in that order."

During 12 years in Congress he never authored a single bill, but he did become a prominent advocate for banning abortion, defunding Planned Parenthood and restricting marriage only to heterosexual couples. In his one term as governor he overstepped when he signed a bill -- the so-called Religious Freedom Restoration Act -- permitting discrimination against gay people, and was forced to seek a change in the law.

His rhetoric attacking abortion rights, adultery and even evolution (he says he doesn't believe in it) assured the Christian right that he was one of them.

When Trump offered Pence his spot on the ticket, the Republican Party's evangelical wing was over the moon. Pence was also a first-term governor facing a tough battle for re-election despite a longstanding and substantial GOP advantage in voter registration. His outspoken support for the Religious Freedom Restoration Act had alienated some centrist Republicans and, though Pence was genial enough, he was not the kind of campaigner who got folks fired up.

Offered a path out of struggling obscurity in Indiana, Pence didn't need a Bible prophecy to tell him it was OK to take the leap. He hitched his pious ambitions to a crude, thrice-divorced, self-confessed sexual predator whose grasp of faith and Scripture appears nonexistent.

Pence's favorite Bible verse reads: "For I know the plans I have for you, plans to prosper you and not harm you, plans to give you hope and a future." He cites it when he discusses the opportunities that come his way, and to explain the confidence he brings to politics.

Pence's theology says that God selects in advance which individuals will become believers and rewards their faith regardless of what they do. This belief allows for all sorts of bad behavior, if it can be framed as supporting the ultimate goal of promoting the evangelical agenda.

Pence's loyalty to the President, even after the "Access Hollywood" tape exposed Trump as a serial sexual harasser, baffled many. It was reported at the time that Pence considered trying to replace Trump at the top of the ticket, but in the end he held his place and his tongue. Pence's religion explains that choice, and his decision to abandon many of his previous positions on the issues, such as his opposition to banning Muslim visitors to America.

To understand how a seemingly pious politician such as Pence could join Trump and stick with him requires tracing the long path of his ambition. Pence wasn't always the rigidly moralistic and confident conservative evangelical he professes to be today. But he was, from the beginning of his adult life, a man who thought he was destined for the presidency.

This article is the first in a series of three by Michael D'Antonio and Peter Eisner, the authors of the new book, "The Shadow President: The Truth About Mike Pence."