For her third book about the executive mansion, “First in Line: Presidents, Vice Presidents, and the Pursuit of Power,” former White House correspondent Kate Andersen Brower spoke to every living vice president. Well, every veep except one, that is.

Mike Pence, currently serving as President Trump’s right-hand man, canceled on Brower — twice.

The author tried to persuade Pence’s staff to let her sit down with the former governor of Indiana. She’d already talked to the other six men who had held the title of VPOTUS. “I don’t want to leave you guys out,” Brower recalled telling Pence’s gatekeepers. But they wouldn’t budge. The narrative was too tricky, especially after reports that Pence was looking to position himself for a 2020 bid for the office down the hall.

“They are very tight-lipped, and they’re smart about it,” Brower said, adding that Pence’s staff has assumed a “damned if you do, damned if you don’t” stance on profiles and one-on-one interviews. “If it seems like he’s doing a lot, then the president won’t like that,” she said.

But Brower did manage to get plenty of juicy gossip for her book, even without the help of the current White House staff.

For one, she learned that Pence and former vice president Joe Biden get on the phone at least once a month, a rare line of communication between two disparate administrations. And according to Pence’s older brother, Greg, Trump reminds the vice president of his domineering father, Korean War veteran Edward Pence Jr.

“You always knew where you stood with my dad,” Greg Pence says in the book. “He was very direct. He just said what he thought, period.”

When it came to Pence’s selection as a running mate in 2016, the entire Trump family powwowed at their golf club in Bedminster, N.J., to make a final decision. It was first lady Melania Trump who announced that whomever they chose had to be “clean.”

“That meant no affairs and no messy financial entanglements,” Brower writes in the book. “In short, it meant no drama. She realized that her husband had a surplus of that already.”

There is one tidbit, involving a former veep, however, that didn’t make it into “First in Line,” which hits shelves June 5.

At a recent salon at the German ambassador’s residence, Brower learned that Walter Mondale, who served in the White House during the Carter administration, delivered an important message to the diplomat.

Ambassador Peter Wittig recalled that after German Chancellor Angela Merkel’s awkward visit to the Oval Office in March 2017 (when Trump famously ignored calls to shake the fellow head of state’s hand), he got a phone call from Mondale.

The former vice president offered a mea culpa on behalf of the entire nation, telling Wittig that he wanted to “personally apologize on behalf of the American people” for Trump’s behavior. The ambassador, Brower recalled, said he was very moved.