Strategists affiliated with the campaigns of President Barack Obama and Mitt Romney say they are using that data to try to influence voting habits — in effect, to train voters to go to the polls through subtle cues, rewards and threats in a manner akin to the marketing efforts of credit card companies and big-box retailers.

In the weeks before Election Day, millions of voters will hear from callers with surprisingly detailed knowledge of their lives. These callers — friends of friends or long-lost work colleagues — will identify themselves as volunteers for the campaigns or independent political groups.

The callers will be guided by scripts and call lists compiled by people — or computers — with access to details like whether voters may have visited pornography websites, have homes in foreclosure, are more prone to drink Michelob Ultra than Corona, or have gay friends or enjoy expensive vacations.

The callers are likely to ask detailed question about how the voters plan to spend Election Day, according to professionals with both presidential campaigns. What time will they vote? What route will they drive to the polls? Simply asking such questions, experiments show, is likely to increase turnout.

After these conversations, when those targeted voters open their mailboxes or check their Facebook profiles, they may find that someone has divulged specifics about how frequently they and their neighbors have voted in the past. Calling out people for not voting, what experts term “public shaming,” can prod someone to cast a ballot.

Even as campaigns embrace this ability to know so much more about voters, they recognize the risks associated with intruding into the lives of people who have long expected that the privacy of the voting booth extends to their homes.

“You don’t want your analytical efforts to be obvious because voters get creeped out,” said a Romney campaign official who was not authorized to speak to a reporter. “A lot of what we’re doing is behind the scenes.”

In statements, both campaigns emphasized their dedication to voters’ privacy.

In interviews, however, consultants to both campaigns said they had bought demographic data from companies that study details like voters’ shopping histories, gambling tendencies, interest in get-rich-quick schemes, dating preferences and financial problems. The campaigns themselves, according to campaign employees, have examined voters’ online exchanges and social networks to see what they care about and whom they know. They have also authorized tests to see if, say, a phone call from a distant cousin or a new friend would be more likely to prompt the urge to cast a ballot.

While the campaigns say they do not buy data that they consider intrusive, the Democratic and Republican National Committees combined have spent at least $13 million this year on data acquisition and related services. The parties have paid companies like Acxiom, Experian and Equifax, which are currently subjects of congressional scrutiny over privacy concerns.

Vendors affiliated with the presidential campaigns or the parties said in interviews that their businesses had bought data from Rapleaf or Intelius, companies that have been sued over alleged privacy or consumer protection violations.

The preoccupation with influencing voters’ habits stems from the fact that many close elections were ultimately decided by people who almost did not vote. Each campaign has identified millions of “low-propensity voters.”

Persuading such voters is difficult, political professionals say, because direct appeals have already failed. So campaigns must enlist more subtle methods. In particular, according to campaign officials from both parties, two tactics will be employed this year for the first time in a widespread manner.

The first builds upon research into the power of social habits. The Obama and Romney campaigns, as well as affiliated groups, have asked their supporters to provide access to their profiles on Facebook and other social networks to chart connections to low-propensity voters in battleground states like Colorado, North Carolina and Ohio.

When one union volunteer in Ohio recently visited the AFL-CIO’s election website, for instance, she was asked to log on with her Facebook profile. Computers quickly crawled through her list of friends, compared it to voter data files and suggested a work colleague to contact in Columbus. She had never spoken to the suggested person about politics, and he told her that he did not usually vote because he did not see the point.

“We talked about how if you don’t vote, you’re letting other people make choices for you,” said the union volunteer, Nicole Rigano, a grocery store employee. “He said he had never thought about it like that, and he’s going to vote this year. It made a big difference to know ahead of time what we have in common. It’s natural to trust someone when you already have a connection to them.”

Another tactic that will be used this year, political operatives say, is asking voters whether they plan to walk or drive to the polls, what time of day they will vote and what they plan to do afterward.

The answers themselves are unimportant. Rather, simply forcing voters to think through the logistics of voting has been shown, in multiple experiments, to increase the odds that someone will cast a ballot.

“Voting is habit-forming,” said David W. Nickerson, a professor at the University of Notre Dame and a co-author of a study of such tactics. Nickerson is engaged in electoral work, though he would not specify for which campaigns or party. “When someone is asked to form a mental image of the act of voting, it helps trigger that habit.”