When Hillary Rodham Clinton arrives in Iowa next week as a candidate for president in 2016, every statement, gesture, laugh, outfit, facial expression and interaction with voters will be put under a microscope the likes of which few, if any, previous candidates have experienced.

Her every step will be analyzed for signs of change or continuity. Has she learned from her loss to then-candidate Barack Obama in the 2008 primaries? If so, what? Does she act entitled or hungry? Has she shifted on foreign policy issues since she was Obama's secretary of state? Are her economic views the same as Obama's or Bill Clinton's or Elizabeth Warren's? Does she appear to like campaigning or see it as a necessary duty to reach her ultimate goal? Is she rusty or sharp, chilly or warm? The list is endless.

Two questions above all others hover over her candidacy: Why does she want to be president? And will voters find her honest, authentic and empathetic enough to entrust her with their futures?

She begins her campaign in a politically dominant yet personally diminished position. She has no serious challengers for the Democratic nomination, yet many Democrats say they hope for real competition, whether to provide direction for their party or to prepare her for the general election. She leads her potential Republican rivals in some, but not all, polls, though those polls are not reliable predictors, given how early it is in the race.

At the same time, she is less well liked — and by a considerable margin — than she was two years ago as she was leaving the administration. That is to be expected, given the rhythms of campaign cycles, but nonetheless it's something worrisome that she cannot ignore.

As secretary of state, she floated above politics and her favorability ratings rose with her. Back in the trenches in the past two years as a prospective candidate and amid controversies over some of her own statements and the uproar over her private e-mail account, she has lost altitude. She must arrest that movement, if she can, as she moves around the country as a candidate.

She will receive plenty of advice, from her advisers and the world at large, about how to answer the question of why she wants to be president. The cover of the latest issue of the Economist magazine features a picture of her with the words, "What does Hillary stand for?" As she assembled a campaign team, she has presumably been thinking about what to say about all that. It is what everyone wants to know.

Yet so much is known already. There is a decades-long resume that offers answers, a record of battles fought and won or lost that point to priorities: women's and children's issues; economic policies somewhat to the left of her husband's but not as far left as progressives would like; a focus on the middle class; a belief in education standards but caution about too much reform; a muscular foreign policy, including a vote for the Iraq war resolution that still rankles some in her party.

The unknowns are unknown in part because there are few easy answers to some of the questions people want answered. Exactly what is a 21st-century economic plan that can do something about stagnant wages and the lack of economic mobility? Clinton and her Republican rivals face the same quandary on this. It is easy to identify the problems, but difficult from either the left or the right to present plausible alternatives to each party's old policies.

Clinton's history suggests no big-bang solution to these profound problems, but rather it shows a wealth of smaller initiatives that, however worthy or potentially effective, are not the stuff of grand or uplifting campaign rhetoric. That makes the challenge of answering the question about why she wants to be president all the more difficult. Almost no matter what she offers, people will want more — more specificity, more originality, more inspiration.

In that sense, there will be no new Hillary Clinton on the campaign trail beginning this coming week. She is a fully formed politician, with a lengthy résumé of accomplishments and considerable baggage from a lifetime of political battles. The question of whether there is a new Clinton may preoccupy much of the commentary about her latest candidacy, but it is something of a diversion. Anyone looking for definitive proof probably will be disappointed.

That doesn't mean voters don't deserve answers to their questions. Economic insecurities and international conflicts demand that candidates for president listen to and respond to the concerns of the voters — not merely through the filter of focus groups conducted by campaign strategists, but by direct contact and conversation that can be experienced only through ground-level campaigning.

Clinton has plenty of knowledge about the issues, as well as the capacity to command as much outside expertise as she needs. She can offer lots of white papers on different policies. In late 1991, her husband delivered three speeches that outlined both the New Democratic philosophy and the details of the policies that he wanted to pursue. These were wrapped in a bundle called the New Covenant, and they laid the foundation for his successful presidential campaign.

Few expect Hillary Clinton to do anything quite that ambitious this year, but she will no doubt want to lay out an updated vision from her first campaign, as well as from the presidencies of her husband and Obama. She will need to stake out her ground.

Where Clinton's candidacy is likely to rise or fall is on how the American people respond to her personally. She is a divisive and polarizing figure — not just because of her own history but because that is the nature of politics in this period of history. She can't completely erase that, but her task will be to offer reassurances to voters who are at least open to her candidacy but who nonetheless have questions or reservations about who she really is.

This demands more than a biographical reintroduction for someone described as the least-known well-known woman in the world. She talked regularly in her first campaign about her own biography, her Midwestern roots, her mother and father and life in the Chicago suburbs and beyond.

She may do that again, but the questions voters have about her go beyond where she came from. Her initial trips will be watched for what she says and how she says it. Another measuring stick should be how well she listens and what she learns from the voters. Can she identify what people really want to know about her as a possible president and supply answers they find credible? That is the challenge as she starts the campaign.