Story highlights Taking stock, President Barack Obama realized he had unexpected strong suit

George W. Bush made barnyard reference to Rick Perry

Romney campaign got blunt advice from Chris Christie

Some Republicans hoped late entry into race could replace Romney

"Double Down," a behind-the-scenes account of the 2012 presidential race by the journalists Mark Halperin and John Heilemann, is out Tuesday. It's the sequel to "Game Change," their 2008 campaign retrospective that became an HBO film by the same name.

The authors, self-styled ringmasters of Washington's political media "Freak Show," are skilled at creating buzz, packing their book with provocative tidbits and a range of splashy scoops -- an impressive feat considering that the Barack Obama-Mitt Romney showdown was the most scrutinized national campaign in American history.

The book has already made headlines: The Obama campaign flirted with the idea of kicking Vice President Joe Biden off the ticket and replacing him with Secretary of State Hillary Clinton , and the Romney campaign was startled by what it dug up on Chris Christie in the process of vetting him to be the Republican vice presidential nominee.

But here are 10 other newsmaking items from the book that has Washington transfixed:

1. Obama: 'I'm really good at killing people'

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In late 2011, President Obama, "an inveterate list maker," began writing up a list of his achievements on a yellow legal pad. Writing his thoughts down on paper "helped him to quiet his mind." The purpose was to help himself and his advisers reason through the best ways to present his three-year track record to voters.

On September 30, the same day a Predator drone strike killed the American-born cleric Anwar al-Awlaki, Obama presented a small stack of yellow legal pages to his aides gathered in the White House's Roosevelt Room.

"Obama didn't need to run through this preamble," the authors write. "Everyone knew the litany of his achievements. Foremost on that day, with the fresh news about al-Awlaki, it seemed the president was pondering the drone program that he had expanded so dramatically and with such lethal results, as well as the death of bin Laden, which was still resonating worldwide months later.

" 'Turns out I'm really good at killing people,' Obama said quietly. 'Didn't know that was going to be a strong suit of mine.' "

2. Obama's secret George Soros summit

Obama's distaste for the ring-kissing demands of campaign fundraising is the stuff of legend among Democrats, so it's no surprise that a meeting with liberal megadonor George Soros in 2010 came up empty.

In September 2010, the White House arranged "a secret summit" between the president and Soros at the Waldorf Astoria in New York, "in hope that Soros would be induced into serious check-writing on behalf of the Democrats ahead of the midterms."

Soros lectured Obama for 45 minutes on the economy. Obama, the authors write, "was annoyed and bored."

"Afterwards, he fumed, 'If we don't get anything out of him, I'm never f--king sitting with that guy again.' "

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As for Soros, the hedge-fund titan declined to pony up in any big way for the midterms.

3. George W. Bush called Rick Perry 'chicken-s--t'

After Texas Gov. Rick Perry jumped into the Republican presidential race, long-standing tensions between him and the Bush family began to burst into view. Perry wasn't shy about criticizing the patrician roots of George W. Bush, his gubernatorial predecessor in Texas. Longtime Bush adviser Karl Rove, who thought Perry was unelectable, fired back at Perry

Publicly, the Bush clan claimed not to be offended by the sudden rise of Perry. But privately, Barbara Bush "was hyperventilating over Perry" up in Kennebunkport, Maine. And her son "was steaming."

"At a dinner party in Washington, the 43rd president vented to a Romney ally. "You can't take Perry seriously," Bush said, according to the authors. "He's a chicken-s--t guy."

4. Chris Christie on Newt Gingrich: 'He's a joke'

After the once-fading Newt Gingrich returned with gusto in South Carolina and trounced Romney in the Republican primary, Romney's campaign was forced to recalibrate and develop a game plan to eliminate Gingrich in Florida.

Gov. Chris Christie of New Jersey called Romney to give him some advice.

"Get out of your crouch and kick the s--t out of this guy," Christie said. "That's what you should do. He's a joke. And you're allowing him to be taken seriously."

Romney went on to trounce Gingrich in the Florida primary, drowning him in attack ads.

5. The white-knight scenario

In the darkest days of Romney's Republican nomination fight, facing down a surprisingly robust conservative challenge from former Sen. Rick Santorum before the Michigan primary, Haley Barbour was alarmed.

The former Mississippi governor, one of the Republican Party's most well-connected and well-respected insiders, worried that Romney was so feeble as a candidate that he would be unelectable once the general election rolled around.

So he consulted with Scott Reed, a veteran GOP fixer, about the "white-knight scenario" -- recruiting a stronger candidate who could seize the nomination with a late entry into the race and a brokered convention in Tampa, Florida. Reed began investigating filing deadlines and ballot access rules for late primary states, circulating the details to Republican grandees around Washington. House Speaker John Boehner "was warm to the notion."

And Barbour went even further. In Washington, he sat down with Christie and Indiana Gov. Mitch Daniels -- two Republicans who had declined previous entreaties to enter the race -- and asked them to reconsider. Both gave it serious thought but ultimately declined.

6. The Clinton ransom

Keenly aware of Bill Clinton's popularity among Democrats and his comfort talking about middle-class issues, Obamaland worked overtime to get the 42nd president involved in the campaign.

But it wouldn't come without a price.

Clinton's then-gatekeeper, Doug Band, "issued an ultimatum to the Obamans: the price of WJC's involvement in the campaign was the retirement of HRC's balance due."

In other words, Band was demanding that Obama help pay off Hillary Clinton's 2008 campaign debt -- at that point, about a quarter of a million dollars -- in exchange for Bill Clinton's help on the trail.

Though top members of the Obama campaign were flabbergasted at the demand -- and held Band in especially low regard, calling him a nickname unfit for printing here -- they eventually agreed to help retire Clinton's debt.

7. The Ricketts plan

The story landed like a hydrogen bomb: The New York Times reported in May 2011 that Republican billionaire Joe Ricketts, the TD Ameritrade founder and Chicago Cubs co-owner, was proposing an eye-popping $10 million ad campaign designed to dredge up the 2008 controversy surrounding Obama's former pastor, Jeremiah Wright.

The Obama campaign was furious that Republicans would consider playing the race card. But it turns out that Obamaworld was behind the story.

The Ricketts plan, it seems, was anonymously dropped off at the Chicago offices of Democratic direct-mail vendor Pete Giangreco by "a mystery brunette" carrying a manila envelope. Just who leaked it remains a mystery, Halperin and Heilemann write.

Giangreco promptly rushed over to Obama's Michigan Avenue headquarters to hand off the document to Obama campaign manager Jim Messina. Obama high command then decided to slip the Ricketts plan to the media, in hopes of killing it with negative publicity before it could even get off the ground.

"The Obamans didn't want their fingerprints on the disclosure, so they used a third-party cutout to funnel the Ricketts document to The New York Times," the book reveals.

It worked. All hell broke loose, and the Obama rapid response operation had a field day prodding reporters to get Romney to disavow the proposed ad campaign and anything related to Wright.

8. The Eastwood 'car crash'

Clint Eastwood's rambling, incoherent, off-the-cuff speech-turned-performance-art appearance at the Republican National Convention caused heads to explode backstage.

Once Russ Schriefer, the campaign's point person for convention planning, began to wrap his head around the scale of the disaster before him, "he was in a state of panic."

"Rushing backstage to the control room to try to give Eastwood the hook, he ran into [Romney adviser Stuart] Stevens -- who started screaming, 'This is terrible! It's a car crash!' "

According to the authors, "Stevens lost all control. He was throwing things, howling, cursing, and weeping, until he dropped his head into his hands."

Stevens also excused himself, made his way to another room, and vomited.

9. 'Project Goldfish'

Romney's search for a running mate began in April 2012 with about two dozen names compiled by his longtime adviser Beth Myers, who presided over the vice presidential search, code-named "Project Goldfish" after the snack food.

Presented with the initial list, Romney narrowed his possible choices down to 11 Republicans: New Hampshire Sen. Kelly Ayotte, Texas Sen. John Cornyn, New Jersey Gov. Chris Christie, Indiana Gov. Mitch Daniels, former Tennessee Sen. Bill Frist, former Arkansas Gov. Mike Huckabee, Virginia Gov. Bob McDonnell, former Minnesota Gov. Tim Pawlenty, Ohio Sen. Rob Portman, Florida Sen. Marco Rubio and Wisconsin Rep. Paul Ryan.

After sorting through "preliminary research" on each of them, the Republican nominee drilled down on five final choices: Christie, Pawlenty, Portman, Rubio and Ryan. In keeping with the "Project Goldfish" theme, each potential running mate was given a code name. Christie's was "Pufferfish."

Once a larger group of advisers were brought into the process, "the overwhelming consensus" was for Ryan, who was eventually picked. Romney adviser Stevens, though, was "adamantly in favor of Christie."

But Romney and Myers ultimately concluded, based on research compiled by attorneys on the vetting team, that Christie's background was "littered with potential landmines" -- and they pulled the plug on Christie.

10. The Huntsman debacle

Among the GOP cast of characters, no one emerges more sullied than Jon Huntsman, whose shameless ambition wilts under the grueling spotlight of a national campaign and clashes with his own staff.

As Obama's ambassador to China, Huntsman apparently circumvented the Hatch Act -- which prohibits high-ranking U.S. officials from engaging in partisan political activity -- by using his wife, Mary Kaye, as a back channel to plot embryonic campaign strategy with John Weaver, his adviser-in-waiting back in the States.

In the fall of 2010, the authors write, "Mary Kaye began e-mailing Weaver and asking about 2012. Sometimes two or three times a day the missives hit his inbox: What's the state of the race? Who's in? What do you think? She referred to her husband as "HE," a code that probably would not have provided much protection had the communications been exposed."

Once a candidate, Huntsman and his family were taken aback by the drudgery of campaigning, particularly fundraising. They were also mortified by the fire-breathing anger of the tea party.

Instead, the Huntsmans were "like candle-drawn moths to the liberal glitterati," cozying up to New York celebrities like Tina Brown, Arianna Huffington and Diane Von Furstenberg who 'made them swoon.' "

Mired in low single digits in national polls, Huntsman also decided at one point to abandon his Republican bid and run as an independent, but he was talked out of it by his family.