I envy Hillary Clinton's ability to keep her cool. I wish I knew how she does it.

When she walked, characteristically beaming and waving, onto the Des Moines Area Community College stage with Tom Vilsack last week in Des Moines, Iowa, it was as if the previous week's testy exchange at a Las Vegas press conference had never happened. You wouldn't imagine that newscasts were being led by stories of the FBI probe involving her handling, as secretary of state, of classified emails. You'd find it hard to believe the steady drumbeat about the Democratic frontrunner's falling poll numbers.

And you certainly wouldn't pick up, from the glowing introduction by the U.S. agriculture secretary, that a fidgety party establishment was casting about for a different standard bearer to run for president - in case these problems blow up in Clinton's face.

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Clinton would never let that show.

Of her many attributes Vilsack highlighted, one is hard to argue with.

"I know of no one in America today that's tougher or more tested than Hillary Clinton," he said, adding provocatively, "You don't have to worry if she's tough enough to handle trumped-up charges. That's with a small 't.'" That sort of quip is actually signature Clinton - making light of something she's been challenged by. She did it in comparing Snapchat to her disappearing emails, as if it's all a joke and she gets the last laugh. She got snippy after a Fox News reporter asked if she'd tried to wipe her computer clean of emails. "What, like with a cloth or something?" Clinton scoffed.

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It's an attitude thing: Like Donald Trump, Clinton really believes she's right. Also, like him, she can make mocking retorts others of us would never dare try. As one who agonizes after being proven wrong on something, I relate more to Rick Perry, who responds with a self-conscious "Oops," rather than an inpatient, "What difference does it make!" Some see it as arrogance, others as self-assuredness, a quality our cultures have made easier for men than for women to adopt. That's part of what makes Clinton such a role model to many women. She has an amazing ability to fall down and get back up, just as snappy and confident as ever. When she said last Wednesday that America should work "for everyone who's ever been knocked down but refused to be knocked out," she knew what she was talking about.

Clinton makes a compelling case for her priorities, striking different attitudes for different occasions. In Ankeny, Iowa, she was pragmatic, laying out problems facing rural America that are seldom talked about: alcohol and drug addiction, the decline in treatment programs and the declining life expectancy of rural women, who die younger than those in every other industrialized country. Noting factors such as poverty, job loss, smoking, substance abuse and obesity, she asked poignantly, "How can this happen in the richest, most powerful nation?" In Cedar Rapids, Iowa, a few weeks earlier, she used indignation and the tone was feistier. "Republicans still believe in trickle-down economics," she exhorted. "We have been trickled on enough!" Crediting President Barack Obama with shepherding an economic recovery despite taking office when the nation was hemorrhaging jobs, she quipped, "I love it when Republicans attack him by saying it's not going fast enough. I'm just sittin' there thinking, 'You have a lot of nerve! We wouldn't have been there if it hadn't been for those terrible policies.'" She knows how to strike a chord, but Clinton also leaves herself susceptible to criticism. As one commentator pointed out when she shrugged off the FBI investigation as politically motivated, the agency is part of a Democratic administration in which she was a high-ranking official. I really don't know how consequential this email thing is, but it feeds into a narrative that the Clintons, both Hillary and Bill, answer to their own rules.

An example: We've come to expect presidential candidates to arrive in Iowa soon after announcing, to tell us what they're about. But for a long time Hillary Clinton refused to address public gatherings here, confining herself to small groups where she did the questioning. She seemed almost to be thumbing her nose at the process, the public and the press.

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Trump showed the same attitude in denying admittance to Des Moines Register reporters in retaliation for a harsh editorial about him. He avoided the Iowa State Fair soapbox stage, where other candidates made their case - other than Hillary Clinton, that is. She kept walking, pork chop in hand, making it clear she's calling the shots.

But she may not understand why Bernie Sanders is cutting into her lead. She may not see how the Vermont senator's consistently red-hot rhetoric on income inequality is drawing crowds and firing people up in a way her differently tailored efforts to appeal to different groups don't seem to be. She said all the right things in Ankeny, but the attendance was low and the applause far from raucous.

Clinton's past efforts on behalf of women, children and health care have demonstrated her empathy in a way that her presidential campaigns don't. They come across as strategic rather than passionate. Even when she tries to fix that deficit by talking about her grandchild, it seems forced, beside the point.

For all the bluster that comes out of Trump, and for however reprehensible some of it is, he says what's on his mind. But Clinton seems so intent on being in control that she's refusing to show where her heart really is. And that's leaving some of us wanting.

Rekha Basu is a columnist for the Des Moines Register.