Presidential campaigns are always studies in contrast, but rarely have the differences between the two major party nominees — and the kind of campaigns they plan to run — been as stark and as unusual as those between Hillary Clinton and Donald Trump.

His political instincts are as rash as hers are cautious. Her policy proposals are as detailed and numerous as his are broad and few in numbers. Her public appearances are controlled and careful. His are the political equivalent of “The Truman Show.” She says he is unqualified to be president. He says she is unfit to serve.

There are certainly ideological differences between the two. But this is not an election that presents voters with the kind of choice they had in 2012. President Obama and former Massachusetts governor Mitt Romney had sharply different views about social and cultural issues, the size and scope of government, the best ways to create jobs, and projecting U.S. power abroad.

Some Democrats probably would take issue with the suggestion that the ideological divisions between Trump and Clinton are less clear than those between Romney and Obama. The Clinton team will appeal to her base with many of the same arguments Obama used against the GOP nominee four years ago.

But Trump is not Romney. If the policy differences between Clinton and Trump were the same as those between Obama and Romney, conservative intellectuals (and many GOP elected officials) would be far more comfortable with Trump as their presumptive nominee.

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Ideological consistency is not part of his Trump’s political DNA. He has been on various sides of various issues — in this campaign and in past years. He will campaign to Clinton’s right on issues such as immigration, gun rights, abortion and repealing the Affordable Care Act. He will crowd her from the left on things like trade (though she has shifted on that issue), infrastructure spending and the use of military force.

[Trump completes rapid transition to pro-gun candidate]

That’s only a small part of what makes the coming campaign so intriguing. The ways in which Clinton and Trump will run their campaigns could be as defining as where they stand on this or that issue. A walk through their campaign offices hints at these differences.

Clinton’s headquarters is sprawling in its size and population, projecting a leave-nothing-to-chance philosophy. Her campaign operates out of two spacious floors in a Brooklyn office building that features spectacular views of Lower Manhattan. The quarters reflect some sensibilities of a tech start-up, but with a corporate overlay.

Trump’s campaign headquarters is on a floor of Trump Tower in Midtown Manhattan. The space is small and cramped in comparison to Clinton’s, populated by only a handful of people. The office has an industrial quality to it, having once been used for building sets for the reality TV show “The Apprentice.”

There are plans to expand elsewhere in the building to meet the demands of a presumptive nominee, and Trump has set up a Washington office. But compared with Clinton and by normal standards, the Trump campaign has been a minuscule organization, operating largely from the visceral instincts of the candidate. For a long period of time, the inner circle numbered just five people.

Clinton’s campaign has been built on a foundation of successful recent campaigns, particularly those of Obama in 2008 and 2012. It will have massive organizations in the battleground states — paid staff and volunteers. They will be backed by prodigious amounts of research — polling data, focus group findings, voter data, analytics and modeling — designed to draw a detailed picture of the battleground electorates.

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The campaign is beginning serious analysis of those electorates. In some states where the demographics are more challenging, the Clinton team will seek to persuade undecided or wavering voters to carry the day. In others, such as Florida, where the demographics are more favorable to the Democrats, the campaign probably will focus more on registering those who haven’t participated in the past and then mobilize every possible Democratic voter to turn out.

[Trump past tax return showed he paid nothing]

Trump consumes and spouts polling data around the clock, using it as a justification for his candidacy and how he conducts himself. Yet he has just now hired a pollster, having rejected the need for one in the primaries. He shows little personal interest in the need for the kind of data and analytics now considered a requirement of modern campaigns.

His expanded team is building state organizations and deepening ties with the Republican National Committee for additional muscle. But his get-out-the-vote operation may never be as comprehensive as Clinton’s, although his advisers say their primary state organizations were better and deeper than they’ve been given credit for.

Where the real differences will come into play are the campaign and communication skills of the candidates. Trump has broken rules in the primaries and shows little inclination to change. He is indiscriminate in doling out interviews — he talks to everybody all the time — and is both strategic and undisciplined about the way he communicates. Clinton is far more controlled, parceling out television interviews and avoiding real interactions with the reporters who have been traveling with her for the past year.

Trump will dominate the hourly news cycle conversation and will be merciless in his attacks on Clinton, as he was against his Republican opponents. Her advisers are not convinced that what worked for him in the primaries will be successful with the broader electorate. They have been studying him, culling information from those who know how he operates as a way of determining the most effective ways of responding. They aren’t sure they’ve cracked the case.

Clinton will not be the main respondent to Trump. Though she has begun to attack Trump in her campaign appearances, campaign officials and surrogates will carry most of the load of answering back as needed. Whether that can break through in an environment in which Trump’s voice speaks loudly is the issue.

Clinton will focus on what she would do to make people’s lives better — a message that has generated little excitement during the primaries. To the extent she talks about Trump, her message will be the obvious: that a Trump presidency is too risky in all respects. He will try to blow past all that in an effort to galvanize those voters sick of the status quo and paint her as a representative of a tired past.

Her advisers think she has the discipline and an outer shell tough enough to prevent him from provoking her unnecessarily. In turn, they think she and they can get under his skin and divert his attention from the factors that will determine how people vote. Trump’s team thinks she doesn’t understand the mood of the electorate.

Clinton has never met an opponent like Trump or run in such a campaign environment as the one that will unfold over the next five-plus months. That reality will animate the election and dictate the tone and pace of the campaign — though not necessarily the outcome.