Rep. Steve Scalise, R-Jefferson Parish, speaks at the Southern Republican Leadership Conference at the Pontchartrain Convention & Civic Center in Kenner , La. Friday, Jan. 18, 2019. The two-day event opened Friday.

When trying to decide whether Mike Pence would make a good vice presidential running mate, then-GOP nominee Donald Trump phoned up U.S. House Minority Whip Steve Scalise to ask what he thought of Pence.

Unbeknownst to Scalise when he told Trump he thought the then-Indiana governor was a "great guy," Pence was secretly on the line, according to a book out this week that has sent tongues wagging among Washington, D.C. insiders and other politics aficionados.

"I was an unwitting participant in the vetting of Mike Pence in front of Mike Pence," Scalise, R-Jefferson, is quoted in the book as later musing.

"The Hill to Die On: The Battle for Congress and the Future of Trump's America," written by Politico's Jake Sherman and Anna Palmer, details Congress in the age of Trump – from the president taking office at a point of Republican dominance in 2017 through the 2018 midterm elections, when Democrats seized control of the House.

Scalise, Louisiana's highest-ranking and longest-serving member of the current Congressional delegation, was the Majority Whip during the time the book covers and his presence looms large through many of its chapters. It also covers a time during which Scalise, 54, was critically wounded during a mass shooting as Republicans practiced for a charity baseball game in 2017 – a hardship that raised Scalise's national profile and also brought him closer to Trump.

The book vividly describes what happened on the baseball field that day, Scalise's often uncertain recovery and his eventual triumphant return to the U.S. Capitol. Scalise has recounted the shooting and its aftermath from his own perspective in a book, Back in the Game: One Gunman, Countless Heroes, and the Fight for My Life, released last fall.

The Pence anecdote is one of several that gives insight into the relationship between Trump and Scalise, who the president has frequently described as a close friend and commended for his bravery in surviving the shooting. It also gives insight into how perceptions of Scalise changed after the shooting.

Describing a rebounded Scalise on the mid-term election campaign trail last fall: "Scalise fully inhabited the new identity born from his shooting and his near full recovery: survivor. He was fearless and confident – exceedingly so, confident not only in his own abilities but in his convictions ... He walked through the crowd like a man who had just risen from the dead."

And, as to be expected in a book largely about leadership dynamics in Congress, several sections chronicle what is viewed as a sometimes tenuous relationship between Scalise and now-House Minority Leader Kevin McCarthy, of California – starting with a tour of the Louisiana State Capitol on the day of Bobby Jindal's inauguration in 2008.

Scalise was a member of the Louisiana House for 12 years and the State Senate for a few months until he was elected to succeed Jindal in Congress.

"The two men had by then known each other for almost 20 years – and the pecking order between them had long been established: McCarthy, big dog; Scalise, underling," the book notes. 

From there, they took their own paths up the House GOP ranks: McCarthy as part of the "young guns" calling for new blood in the party, and Scalise staking his place "as an unflinching conservative, the kind of guy ready to fight to the death for policies that caught fire on the right."

Hill to Die On begins with an opening note about the book's sourcing. According to that disclosure, it's based on Sherman and Palmer's 26 months of reporting on Congress in the era of Trump and based on many interviews both on- and off-the-record. 

Follow Elizabeth Crisp on Twitter, @elizabethcrisp.