The authors write that one of Mrs. Clinton’s “senior-most lieutenants” watched her “bitter and befuddled reaction” to her loss in Iowa, and thought for the first time, “This woman shouldn’t be president.” They write that during debate preps, some staff members assigned to Sarah Palin by the McCain campaign discussed the “threatening possibility: that Palin was mentally unstable.” They add that several of Senator John McCain’s lieutenants agreed that if it looked as if their candidate might actually win in November, they would have to discuss how to relegate Ms. Palin “to the largely ceremonial role that premodern vice presidents inhabited”: “it was inconceivable” that “if McCain fell ill or died, the country be left in the hands of a President Palin.”

Image Hillary Rodham Clinton, on the campaign trail in 2008. Credit... Damon Winter/The New York Times

In addition Mr. Heilemann, who works for New York magazine, and Mr. Halperin, for Time magazine, write that Mrs. Clinton, encouraged by her husband and aides, considered running for president in 2004 but ended up listening to her daughter, Chelsea, who argued that she needed to finish her Senate term. They write that Mr. Clinton and George W. Bush “spoke more often than almost anyone knew”  that “from time to time, when 43 was bored, he would call 42 to chew the fat.” And they assert that Mrs. Clinton blew an opportunity to win the endorsement of Caroline Kennedy, who, they say, had been “dreading a call from Hillary” asking her to go to Iowa on her behalf, knowing, the authors write, that “once she had campaigned for Clinton, siding with Obama would be off the table.” Instead of making the call herself, Mrs. Clinton had one of her staffers phone Ms. Kennedy, who ducked the call.

In another passage, which was widely reported over the weekend, Mr. Halperin and Mr. Heilemann write that the Senate majority leader, Harry Reid of Nevada, encouraged Mr. Obama to run early on, arguing that “the country was ready to embrace a black presidential candidate, especially one such as Obama  a ‘light-skinned’ African American ‘with no Negro dialect, unless he wanted to have one.’ ” Over the weekend Mr. Reid called the president to apologize for his choice of words. Other senators, including Charles E. Schumer, Byron L. Dorgan, Ben Nelson, Bill Nelson, Barbara Boxer and Edward M. Kennedy, the authors add, were also nudging Mr. Obama, then a senator, to take the plunge, though most would “root for Obama secretly,” as they feared retribution from the Clintons should Mrs. Clinton eventually prevail.

Mrs. Clinton, long the front-runner in the race, was so confident of winning, Mr. Heilemann and Mr. Halperin write, that she went so far as to start thinking about her choice of a running mate in fall 2007: she “had already determined without a sliver of doubt that she was not going to choose Obama,” they say, and told her aides that Evan Bayh, Joseph R. Biden Jr., Tom Vilsack and Ted Strickland were at the top of her short list. Around the same time, they write, Mrs. Clinton asked her friend Roger Altman, deputy Treasury secretary in her husband’s administration, to lead a secret project  planning her transition to the White House based on the assumption that a year later she would win the general election.

Mr. Heilemann wrote incisively about Mrs. Clinton in the pages of New York magazine  chunks of his reportage and analysis, taken directly from his articles, appear in this book  and there is more revealing material about her and Mr. Clinton in this volume than the other candidates and their wives. The authors not only dissect the dysfunctional, conflict-ridden Clinton campaign  something that has already been done in detail by many other reporters  but they also emphasize that communication difficulties between the Clintons exacerbated that campaign’s problems.