FLASHBACK: Pence is VP thanks to trick played on Trump by campaign chair targeted in Russia probe
Mike Pence speaks to ABC News (screen grab)

Prosecutors are reportedly preparing to indict former Trump campaign chairman Paul Manafort -- who tricked his boss into choosing Mike Pence as his running mate.

Donald Trump initially offered the vice president slot to New Jersey Gov. Chris Christie, but he withdrew the invitation in favor of Pence a week before the Republican National Convention.

Christie begged Trump for the running spot on July 12, 2016, according to the New York Post, which reportedly bothered Manafort -- who arranged for a last-ditch meeting the following day with Pence, then Indiana's governor.

Campaign sources told the Post that Manafort told his boss the plane had a mechanical problem, which forced Trump to spend another night in Indianapolis, where Pence made his case over dinner.

“Trump had wanted Christie but Bridgegate would have been the biggest national story,” a campaign source told the newspaper. “He’d lose the advantage of not being corrupt.”

He agreed to name Pence his running mate the following day and told Christie it would "tear my family apart" if he picked as running mate.

Manafort and Trump's two eldest sons, Donald Jr. and Eric, along with GOP leaders, pressured the former real estate developer and reality TV star to pass over Christie in favor of Pence.

Trump preferred the deferential Christie, but his advisers argued that Pence would boost him among the evangelical Christians who spurned him during the GOP primaries.

Manafort left the campaign the following month over his alleged ties to Russia, and those ties have remained under scrutiny by both special counsel Robert Mueller and congressional investigators.

This wouldn't be the last time Pence took over a job Christie believed was his.

Pence took over from Christie as head of the Trump transition team Nov. 11, just three days after his stunning election win over Hillary Clinton.

The vice president-elect oversaw the selection of Cabinet officials and other top White House posts -- including the Nov. 17 selection of Mike Flynn as national security adviser, despite a warning the following day by Rep. Elijah Cummings (D-MD) about possibly improper foreign contacts.

Flynn resigned less than a month into the job, after his undisclosed contacts with the Russian ambassador were revealed.

Pence publicly insisted those contacts were "strictly coincidental," and he later claimed not to know Flynn was under investigation for his paid lobbying work for Turkey.

Manafort did not play a role in the transition, but federal investigators wiretapped his phone under a secret court order before and after the election -- when he was known to have spoken to Trump.

It's not clear whether he spoke to Pence during that period.

Trump's two eldest sons and eldest daughter were part of a 16-person advisory committee during the transition, which was directed by Rick Dearborn -- who sent an email seeking to connect top campaign officials with Russian President Vladimir Putin.

That email came in June 2016, when Donald Trump Jr., Manafort and Trump son-in-law Jared Kushner met at Trump Tower with a Russian lawyer who promised damaging campaign information about Clinton.

Dearborn, now Trump's deputy chief of staff, previously served as chief of staff to hen-Sen. Jeff Sessions, who angered the president by recusing himself from the Russia probe over his own undisclosed contacts with ambassador Sergey Kislyak.

The longtime Sessions aide helped to arrange an April 2016 campaign event at the Mayflower Hotel, where Trump promised Kislyak and others in attendance to thaw relations between the U.S. and Russia.

Those contacts all remain under investigation by both federal and congressional investigators.