EXCLUSIVE:This story is adapted from The Matriarch: Barbara Bush and the Making of an American Dynasty, which will be published April 2 by Twelve Books. Author Susan Page, the Washington Bureau chief of USA TODAY, spent hours interviewing the former first lady during the final six months of Bush's life and was given access to her personal diaries spanning decades.

Barbara Bush blamed Donald Trump for her heart attack.

It wasn’t technically a heart attack, though she called it that. It was a crisis in her long battle with congestive heart failure and chronic pulmonary disease that hit her like a sledgehammer one day in June 2016. An ambulance was called to take her to the hospital. The two former presidents who had been at home with her that day, her husband and her oldest son, trailed in a car driven by the Secret Service. The tumultuous presidential campaign in general and Trump’s ridicule of son Jeb Bush in particular had riled her. “Angst,” she told me.

Afterward, Jeb, whose presidential campaign was already history, urged her to let it go, to focus on herself and have faith in the country.

“There’s just a lot of angst” among those distressed by President Trump’s leadership, Jeb Bush told me, using the same word that his mother had used. “So I think one of the solutions is don’t watch it; don’t obsess.”

“Jeb said, ‘Mom, don’t worry about things you can’t do anything about,’ ” Barbara Bush recalled. “He’s right. Just do good, make life better for someone else.”

How did she think things were going in the USA in the Age of Trump?

"I'm trying not to think about it," she said in an interview as the first anniversary of Trump's election approached. "We're a strong country, and I think it will all work out.” Even so, she was dismayed by the nation’s divisions and by the direction of the party she had worked for, and for so long.

Did she still consider herself a Republican?

In an interview with me in October 2017, she answered that question yes. When I asked her again four months later, in February 2018, she said, "I'd probably say no today."

That was a stunning acknowledgment. Barbara Bush had been one of the most recognizable faces of the Republican Party through two presidencies. She was the matriarch of one of the GOP’s leading families. But after Trump’s rise, she saw it as a party she could not continue to support, a party she no longer recognized – even as one of her grandsons, George P. Bush, was on the ballot as a Republican running for re-election as Texas land commissioner.

Her comment reflected the aftershocks of the earthquake that was the 2016 election.

Barbara Bush:'Still in love with the man I married 72 years ago'

Reluctant for another race

Barbara Bush was reluctant for Jeb to run in 2016, but not because she thought he wasn't up to the job. He had been the serious son. When he and George W. were young adults, nearly everyone viewed Jeb as more likely to be a president.

But she had seen how brutal presidential campaigns and the presidency could be. Her husband lost his bid for a second term, a crushing defeat. Her oldest son left the White House excoriated for pursuing a costly war in Iraq. Jeb would inherit all their baggage, all their enemies, she warned. She sensed a dyspeptic mood in the country, a weariness with the political establishment that would disrupt his path.

Eventually, she campaigned for him. He asked because he was in trouble; he had lost the opening Iowa caucuses and was struggling for traction in New Hampshire. She agreed not only because she would do just about anything for her family but also because she was alarmed by Trump, the rival who was coming on strong for the nomination. She recorded an ad, sitting on a dark set, speaking straight to the camera.

She returned to New Hampshire, the state that had rescued the elder George Bush’s presidential prospects in 1988, to campaign once again. This time, she was 90 years old and using a walker. She pushed it through a New Hampshire snowstorm as she went from event to diner to interview.

“I love my son, and I know that America needs him,” she said in an interview on "CBS This Morning" three days before the primary, sitting side by side with him. “He’s honest, dependable, loyal, relatively funny, good-looking” – she elbowed him good-naturedly – “but funny. He’s got the same values that America seems to have lost. He’s almost too polite. I don’t advise him, but if I gave him advice, I would say, ‘Why don’t you interrupt like the other people do?’ And he does not brag like some people we know.”

She refused to say Trump’s name, but there was no mistaking whom she meant. “I’m not getting into a spitting match with him,” she said. “He can spit further than I can.”

Anchor Norah O’Donnell noted that Trump had ridiculed Jeb Bush for deploying his mother in the campaign. “Just watched Jeb’s ad where he desperately needed mommy to help him,” Trump tweeted. “Jeb—mom cannot help you with ISIS, the Chinese or with Putin.”

“Putin endorsed him, for heaven’s sake,” Barbara Bush erupted. “Putin the killer! Putin the worst! He endorsed Trump! That’s an endorsement you don’t want.”

Trump won the New Hampshire primary. Jeb Bush finished a disappointing fourth. When he did no better in the South Carolina primary 11 days later, he decided to end his campaign. He called his mother. “I just want to let you know I’m heading home,” he told her. “I love you,” she said. Nothing more.

‘The real symbol of greed’

Barbara Bush’s negative opinion of Trump dated back decades.

"The real symbol of greed in the 80s,” she wrote in her diary in January 1990. She had just read a news story about Trump addressing a Los Angeles charity gala, an awards dinner for Merv Griffin hosted by the American Friends of the Hebrew University and attended by Ronald and Nancy Reagan. Trump had needled the former president for the high-priced speeches he delivered in Japan. “I see President and Mrs. Reagan in the audience. Did you have to pay them $2 million?”

A month later, she saved news clippings to show a friend about Trump’s separation from his first wife, Ivana. Their divorce would be finalized in 1992. She noted that Ivana’s allies said the $25 million settlement in the prenuptial agreement she signed wasn’t enough. “The Trumps are a new word, both of them,” she wrote. “Trump now means Greed, selfishness and ugly. So sad.”

George and Barbara Bush: A love story

Trump had made a weird overture to George Bush in 1988, when Bush was poised to clinch the Republican presidential nomination. In his biography of George Bush, "Destiny and Power," historian Jon Meacham reported that Trump told campaign strategist Lee Atwater that he was available to be Bush’s running mate. Writing in his diary, Bush dismissed the idea as “strange and unbelievable.”

More than a quarter-century later, Barbara Bush couldn’t quite imagine that Trump was going to win the White House on his own.

“I don’t understand why people are for him,” she said in one interview. In another, she expressed astonishment that women could support him. George Bush ended up voting for Hillary Clinton, the first time in his life that he had cast a ballot for a Democrat for president. Barbara Bush wrote in Jeb’s name on the last day of early voting. “I could not vote for Trump or Clinton,” she wrote in her diary.

Barbara Bush’s original judgment, made three and a half years earlier, seemed prescient. “There are other people out there that are very qualified, and we’ve had enough Bushes,” Bush declared on NBC’s "Today" show in April 2013, amid speculation about whether Jeb was going to run.

The country apparently did feel there had been enough Bushes, and enough Clintons, in high office. Jeb Bush lost the Republican nomination. Hillary Clinton won the Democratic nomination but lost the general election, trailing Trump in the Electoral College, though she carried the popular vote. “I think people didn’t want anybody who was in office,” Barbara Bush told me. “I think they wanted a whole new world.”

The morning after the election, George H.W. Bush, honoring the traditions of the office, called the president-elect to offer his congratulations. Trump “was very nice,” Barbara Bush wrote in her diary. “He said that George was a great president and he admired us both. He said Jeb was strong and a great man. He is trying ... at this moment ... to be conciliatory. He says he wants to represent all the people.”

Two weeks later, she wrote a warm letter to Melania Trump, who faced intense speculation about whether and when she would move to Washington from New York.

Bush urged her to do whatever was best for her and to protect her son, Barron. She knew the White House could be a lonely place, especially for a child. She gave her some advice, the same advice she volunteered to Clinton in 1992, when the Clintons were preparing to move into the White House with an only child.

Dear Mrs. Trump,

The world thought I was writing this note to Bill Clinton. I am glad that I am not. I wanted to welcome you to the First Ladies very exclusive club. My children were older and there fore I did not have the problems you do. Whatever you decide to do is your business and yours alone.

Living in the White House is a joy and their only job is to make you happy.

If you decide to stay in NYC that will be fine also. When you come to the White House let your son bring a friend. That is my unasked for advice.

God Bless you,

Barbara Bush

Bush also wrote a personal note to Karen Pence on the Christmas card she sent her and her husband, Vice President–elect Mike Pence, soon after the election. “I really wanted to write you earlier to tell you how much fun I had as the wife of the VP,” she told her. “It is a lovely house.”

Sitting in the living room of that “lovely house,” Karen Pence showed me the card, even the envelope saved. She had first visited the house and met Bush in 1988, when Mike Pence was making a bid for Congress and the second lady hosted a reception for the spouses of GOP challengers. A photo of that meeting was in a frame, sitting on the grand piano. At the time, Bush had advised her to move to Washington if her husband won the election. (He didn’t win that time, but he did later, and Karen Pence took her advice.)

'Horror that Trump had won'

Those weren’t the letters Bush had expected to write after the 2016 election. She had drafted a funny congratulatory letter to send to Bill Clinton – assuming that he would take over the role of presidential spouse. “It said, ‘Welcome to the First Ladies Club,’ ” she told me. “ ‘We can’t wait to initiate you.’ ” She never mailed it.

“I woke up and discovered, to my horror, that Trump had won.”

She didn’t hide her horror from those close to her. After Trump was elected, a friend in Kennebunkport gave her a Trump countdown clock as a joke. The red, white, and blue digital clock displayed how many days, hours, minutes and seconds remained in Trump’s term. She parked it on the side table in her bedroom, next to the chair she would sit in to needlepoint or watch television.

She liked the countdown clock so much that when the Bushes returned to Houston that October, she brought it with her. It sat on her bedside table, where she could see it every day. It was there to the day she died.

Susan Page, the Washington Bureau chief of USA TODAY, has covered the past 10 presidential elections and interviewed the past nine presidents. The Matriarch: Barbara Bush and the Making of an American Dynasty, is her first book. Here's information about how to pre-order and the book tour.

Barbara Bush: Lesser-known facts about former first lady