(CNN) - Sen. Majority Leader Harry Reid called then-Defense Secretary Bob Gates in 2008 to say he was considering Gates as a potential running mate for Barack Obama, according to the ex-Pentagon chief's new memoir.
In an exchange recounted on page 262 of the book, "Duty," Reid quizzed Gates on the phone about his political history. Gates was appointed Defense Secretary by former President George W. Bush in 2006 and remained at his post as part of Obama's team of rivals.
The detail is one of many surprising nuggets from Gates' new memoir, which offered scathing critiques of Congress and the Obama administration.
Here's an excerpt from Gates' book about the conversation with Reid:
"It took a lot of willpower for me to keep from bursting out laughing. He asked me if I had a public position on abortion; I laughed, saying no. He asked if I was a longtime Republican. I said, actually no; I hadn't been registered with either party for many years. He asked how long I had been an academic. He wanted us to keep all of this very private between us. "Possibly nothing will come of it," he said. I couldn't figure out if he was serious, if it was just idle flattery, or if he was delusional."
In his book, Gates adds "It was so weird," and says he never told anyone "in part because I didn't think they'd believe me."
A Democratic source tells CNN the phone call was Reid's idea, not the Obama campaign's.
CNN also reached out to Reid's office for comment.
Obama famously went on to choose then-Sen. Joe Biden of Delaware as his running mate in 2008. Others on the short list included then-Virginia Gov. Tim Kaine, then-Sen. Evan Bayh of Indiana, and then-Rep. Chet Edwards of Texas.
Gates' book includes strong criticism of Biden, saying "I think he has been wrong on nearly every major foreign policy and national security issue over the past four decades."
Obama said in a November interview that choosing Biden was "one of the best decisions that I've ever made."
Gates' memoir is set to be released next week.