As Hillary Clinton prepares to run for president, she should remember the words of her husband's campaign theme song in 1992: "Don't Stop" by Fleetwood Mac.

"Don't stop thinking about tomorrow

Don't stop, it'll soon be here

It'll be better than before

Yesterday's gone, yesterday's gone"

As Bill Clinton knew very well, American politics is always about the future, not the past. Yesterday's gone.

Hillary Clinton's new book, "Hard Choices," is a detailed account of her years as secretary of state. But it tells voters little about the questions that concern them the most: Who is she, really? Does she understand their lives? How will she make them better?

Remember, Clinton has run for president before and lost. In 2008, she struggled to find the words and stories that connected with voters on an emotional level.

She lost to Barack Obama, who deeply understood the power of stories and told them very well. And yet even the president, asked by Charlie Rose on CBS about the "biggest mistake" of his first term, gave a revealing answer.

"The mistake of my first term ... was thinking that this job was just about getting the policy right," he said. "And that's important. But the nature of this office is also to tell a story to the American people that gives them a sense of unity and purpose and optimism, especially during tough times."

That's true for candidates as well as presidents. Clinton's book focuses on policies -- toward Russia and China, Syria and Iraq. And of course "that's important."

But it's not how most voters choose a president. They want to gauge her tone and temperament, her character and values. And Hillary Clinton has always faced a warmth gap.

A Wall Street Journal/NBC poll just before the 2008 campaign tried to measure this gap. Fifty-three percent gave her positive marks on "experience and competence," but her rating fell to 44 percent on "values and character" and 39 percent on "warmth and compassion."

Obama was certainly taking a sexist slant when he cracked during one debate, "You're likable enough, Hillary." He was also identifying one of her biggest weaknesses -- then and now.

Likability alone is not enough, however. It has to be combined with the quality mentioned by Obama: the ability to convey "a sense of unity and purpose and optimism."

Look at the three most successful politicians of this era. Ronald Reagan told his favorite story a million times, about the boy who saw a pile of manure and immediately grabbed a shovel, saying, "There has to be a pony in there somewhere."

Corny, yes, but that story captures an essential American quality: a spirit of resilience and hopefulness, "especially during tough times." Bill Clinton learned a lot from Reagan. His campaign video in 1992 was called "The Man from Hope," and he reveled in his "Comeback Kid" nickname.

Obama learned from both of them, adopting the resonant slogan "Hope and Change" and telling countless stories about his mother, who depended on food stamps, or his grandmother, who faced gender discrimination. How often did he and Michelle talk about straining to pay off their student loans?

All those tales made a powerful point: We understand your lives. We've faced the same problems. We're just like you.

By contrast, Hillary in 2008 liked to say, "I grew up in a middle-class family in the middle of America in the middle of the last century." Not exactly "The Man from Hope."

Can she be a better candidate this time around? Can she find the stories that close her warmth gap?

Her book contains a few, such as signing a memo "MOTB," Mother of the Bride, as she juggled plans for daughter Chelsea's wedding while negotiating with China. Or binge-watching the TV series "House of Cards" with Bill.

She also offers a moving tribute to her mother, who suffered through a childhood marked by "trauma and abandonment" and went to work as a housekeeper and nanny at age 14. Expect to hear a lot more about her mother -- and daughter and grandchild -- once the campaign heats up.

But in interviews about the book, she stumbled on a personal question, telling Diane Sawyer on ABC that she and Bill had been "dead broke" after leaving the White House. Technically true, but it opened her to ridicule since the Clintons quickly wiped out their debts by earning millions in book deals and speaking fees.

So the question remains: Can Hillary convince the country there's a pony in there somewhere?

Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com.