Heading into the Democratic convention, and for the entirety of this campaign and her career in Washington, Hillary Clinton’s biggest problem has been that she’s perceived as dishonest.  

By contrast, the public’s nagging worry about Donald Trump is that he doesn’t have the temperament for the presidency. If he tried to undo his selection of Mike Pence as his running mate, would he try to un-launch a nuclear warhead?  

On the surface, it would seem that Trump has the tougher challenge. When comparing presidential candidates, most people would probably pick a liar over a maniac. But scratch a little deeper and Trump’s challenge is less daunting.  

It would take a discipline we haven’t yet seen from the Donald, but he can address his temperament issue. It’s uncomfortable, unnatural even, for Trump to stick to a script written by his handlers, stop taking shots at members of his own party and generally speak as though he expects to someday represent the United States in meetings with foreign leaders. But, even though it’s against his instincts and his id to follow instructions, playing sane isn’t really all that tough.  

It’s not so easy for Clinton. If she’s seen as a liar, she can neither promote herself nor attack her opponent with credibility. When she goes negative, it backfires. When she acts as a validator for herself, it falls on the deaf ears of those who believe she’s deceived them before.  

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Thanks, GOP. XOXO, Hillary

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None of that is to say that Clinton will lose the election. Most voters aren’t persuadable. Most of them know that they’re Democrats or Republicans, and this convention should get Democrats as fired up as they can be for their nominee.  

Presidents Barack Obama and Bill Clinton, Vice President Joe Biden, and Sens. Elizabeth Warren and Bernie Sanders will all give testimonials sure to highlight Clinton’s strengths. They will do so at the peril of Hillary haters finding them dishonest, particularly the Sanders contingent at the convention and watching at home on television.  

The irony is that Trump lies constantly. He’s got so many pants-on-fire ratings from the fact-checking website Politifact that it would be difficult  for him to purchase fire insurance. But if he’s not completely flame-retardant, he’s at least coated in Teflon. His supporters couldn’t care less if he lies, and Clinton has little standing to call him out on his mendacity.  

Since she’ll never convince voters that she’s as honest as Abe, Clinton has to figure out how to make honesty less of an issue in the campaign. Part of that, of course, is what she and her surrogates are doing now: Using Trump’s own words — and those of his fellow Republicans — against him.  

But that’s a pretty typical political trick and this is a nontypical year. She has to find another answer. The best available option is to make voters believe that what Trump says he would do is so anathema to their interests that it’s more important than whether she fudges at the margins.  

That is, the worst lie Hillary could tell is only so bad compared with the reality of a Trump presidency. The first thing she should do is drop the word “I” from her vocabulary. “I am,” “I want to” and “I will” don’t work for her. She should remove herself from the equation. “X must be done,” “X is an American value,” and “Families need X” are much better constructions for her. Even “we,” which is much better than “I,” has risks with voters who might prefer her to Trump but don’t necessarily identify with her.  

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Treating FBI Chief as Villain, a Mistake for GOP

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The second part of the equation is to continue with what has been a strong line of attack against Trump. It started in a speech she made in California in June that infused some of President Obama’s hallmark ridicule. She can’t make Trump into a joke, but she must not waver from reminding voters that she and many others in both parties believe that he would be dangerous to the interests of the United States.  

If this election is about who can be trusted to tell the truth, Clinton’s in trouble. Her contortions over her email scandal — and the FBI director pointing out that things she said publicly weren’t true — have made it impossible for Clinton to claim any high ground or even get out of that rut.  

But if the election is about who can be trusted with America’s interests, she’s in much better shape.  

Roll Call columnist Jonathan Allen is co-author of the New York Times-bestselling Clinton biography “HRC” and has covered Congress, the White House and elections over the past 15 years.