Type in a Google search for the words “immigration reform,” and in the split second it takes for your results to pop up, the president’s reelection campaign may begin courting you. Up comes an ad for barack­obama.com, next to the search results.

And if you take the next step and click through to the campaign’s Web site, ads for the president’s reelection may start following you around the Web.

The Obama campaign, and to a lesser extent its GOP rivals, has embraced the potential of the Internet age to reach possible supporters this election season.

The president’s campaign has bought Google advertising space next to all sorts of searches, including “Warren Buffett,” “Obama singing,” “Obama birthday” and, for basketball fans, “Obama bracket.”

The assumption is that people interested in those topics may also fit the profile of potential Obama backers, making them perfect targets for a strategically placed ad.

The president is not alone in this. Mitt Romney has bought advertising space next to his father’s name, for example, and Rick Santorum has gone for the term “Rush Limbaugh,” according to Hitwise, a company that samples Internet traffic. The ads are rotated on and off the search pages, and campaigns often purchase the ad space for short periods.

Spending for online ads

The Obama campaign is by far the most aggressive in trying to reach voters online, so far spending more on Internet advertising than on television, radio and telemarketing combined. And the president’s campaign has spent five times more on online ads — jumping from $2.3 million to $12.3 million — than at this point four years ago, when he was running against Hillary Rodham Clinton for the Democratic nomination, federal disclosure records show.

The president’s campaign, which would not discuss its Internet strategy, also is more aggressive in using technology that can track and target people based on the Web sites they’ve been browsing, a practice commonly used in corporate advertising.

The candidates are far from abandoning television, direct mail and other marketing strategies, but the competition to find supporters online has rewritten the book on campaigning.

“If you’re not advertising online, you’re missing out on a huge chunk of people and an ability to influence them,” said Tim Lim, a former field organizer for Clinton who runs Precision, an ad firm working with Democratic campaigns.

Still, the practice of tracking and targeting people by their characteristics and their behavior on the Web raises the spectre of intrusion.

“Your browsing and your purchase habits and even the activity of your friends on social networks will influence what a candidate says to you,” said Ashkan Soltani, an Internet privacy researcher who has consulted for the Federal Trade Commission. “It’s great to talk to folks about what they want to hear, but the problem is most people don’t know how deeply personalized it is.”

Consumer advocates for years have raised objections to the sharing of personal data among companies online. And the Obama administration has called for an online “privacy bill of rights” that would mean many of the techniques used by the campaign could soon require more transparency and opt-out provisions.

The Obama Web site explains that data submitted by users in response to surveys will be saved and that the campaign will glean and save other information, such as their locations, computer systems and how they came to the site. The data will be used to personalize messages and might be shared with consultants or other campaigns.

But campaign officials say the list of supporters has not been sold or given away except to Organizing for America, a part of the Democratic National Committee created from Obama’s 2008 campaign.

“As is true with other presidential campaigns, we seek to reach voters with a message that is relevant to them using industry standards of online advertising,” campaign spokeswoman Katie Hogan said. “This campaign has and always will be an organization that takes care to protect information that people share with us.”

More ways to find targets

Since 2008, advertisers have widely adopted technology that permits targeting commercials to specific segments of users as they move through the Internet.

Four years ago, campaigns typically bought ads from a given Web site based on the demographics of its audience. It also was possible to target audiences by their geographic location, for example, or the text visible on Web pages. So if a campaign wanted to target mothers, it might advertise on a site that suggested baby names or on a page with text about parenting.

That strategy remains, with the Obama campaign blanketing national news sites and those that tend to draw left-leaning viewers, including the New Republic magazine’s and the discussion forum DailyKos, according to ad tracking firm Moat.com.

But new technologies allow the campaign to target specific segments of the electorate, no matter where they are browsing. That is possible because companies tag and track most Internet users as they move around the Web.

When users visit Obama’s campaign site, their browsers submit information to more than a dozen outside advertising companies. Then, as the users move on to other sites, their browsers notify some of the same ad companies, which then place Obama campaign ads on the new site.

By comparison, a visit to Romney’s campaign site triggered communication with five ad companies, while Santorum’s triggered four, according to a recent sampling using publicly available software.

The contacts to outside advertisers also allow “behavioral marketing,” through which ad companies use browsing patterns and online surveys to create rich profiles of users, flagging their likely interests, demographic information and, in some cases, their political ideologies. The companies can then place users into categories and offer campaigns the ability to shape their messages for each category.

Some companies have been able to use voter file information to target households with registered voters, even noting which among them are most likely to participate in upcoming elections.

The Obama campaign’s heavy use of the Internet helps explain the increase in support he is getting from donors giving smaller campaign contributions. Those donors often contribute online, using credit cards. One million people donated in the first six months after the campaign launched last year, and the percentage of its funds coming from small donations is higher than it was in Obama’s 2008 campaign.

And those Web users seem to be seizing on a general interest in the president. During the NCAA basketball championships, the campaign bought advertising next to searches for “Obama bracket.” Around the time of his 50th birthday in August, the campaign purchased space next to “Obama birthday” search results, according to Hitwise.

The keywords also extend to more serious topics. The campaign bought space beside “Buffett rule” and “Warren Buffett” to draw supporters looking for information on the president’s proposal to raise taxes on high-income earners, a proposal supported by Buffett, who is a billionaire.

The campaign has bought ad space tied to several keywords related to immigration, an area in which the administration has achieved few of its major legislative goals. A search for “Dream Act” will bring up an ad linking to a special page on the campaign site dedicated to the legislation by that name, which would provide residency for immigrants who arrive in the United States as minors and go to college or serve in the military. The bill is stalled in the Senate.