President Obama has unleashed a particularly unusual fundraiser for his 2012 campaign.

One Internet ad starts with a two-toned blue background, like dozens of other pro-Obama spots. Then the furry star pops into the frame, tongue out and ready to frolic. “Join Pet Lovers for Obama,” the ad implores.

The unlikely pitchman is Bo, the White House family pet, who may well be the first “first dog” to emerge as a central player in a presidential reelection campaign.

Political pets have long attracted inordinate attention, from then-Sen. Richard M. Nixon’s dog, Checkers — the focus of an early 1950s scandal that slowed his political ascent — to Bill Clinton’s adopted stray cat, Socks. In 2004, George W. Bush’s campaign put together a tongue-in-cheek video for the Republican National Convention seeking advice from Barney, Bush’s Scottish terrier, on how to attract the “canine vote.”

But Obama appears to be breaking ground by featuring his Portuguese water dog so prominently in official campaign advertisements and fundraising efforts, part of a broader focus on the president’s family.

The strategy is also an attempt to capi­tal­ize on the persistent controversy over canines that has dogged the 2012 race. Obama’s presumed GOP rival, Mitt Romney, has come under fire from Democrats and animal-rights activists for transporting his now-deceased Irish setter, Seamus, in a crate tied atop the family station wagon for a 12-hour trip to Canada in the 1980s. Republicans, in turn, have highlighted Obama’s recollection in his 2004 autobiography that he had eaten dog meat as a child in Indonesia.

“My stepfather always told me, ‘It’s a boy-eat-dog world out there,’ ” Obama said to laughter at the White House Correspondents’ Association dinner Saturday.

Mark McKinnon, a top Bush campaign adviser, joked that the 2012 race “has gone to the dogs.” But, he added, a candidate’s relationship with animals can serve as an important marker for many voters.

“People look at a whole constellation of attributes when they vote for president,” McKinnon said. “Pet lover may not be high on the list, but it’s on the list.”

For the Obama campaign, pet lovers are just one niche among many, with specific appeals aimed at women, African Americans, students, military families and countless others. The result is a campaign that might be the most micro-targeted in history, attempting to use the power of the Web and social media to reach ever-thinner slices of the electorate.

Nearly half of the Obama campaign’s March budget — $6.7 million — went toward Internet ads, many of them targeting specific demographic or interest groups. Romney has been less aggressive in micro-targeting efforts and has spent only a tenth as much on online advertising.

Pro-Obama Internet ads featuring Bo, which have run steadily in recent months, urge voters to“Bark for Barack” by donating to the campaign. Official “Pet Lovers for Obama” pages on Facebook, Pinterest and other social media sites feature pictures of the president and his dog and invite supporters to share their own pet photos.

The campaign also offers nearly a dozen Bo- or pet-themed products on its Web site, including a $12 “Cats for Obama” collar and a $35 red, white and blue “Obama Dog” sweater. “This adorable Obama dog sweater will keep your furry friend feeling cozy and looking stylish,” the description says.

Other subgroups targeted by the Obama campaign include nurses (featuring bumper stickers, magnets and T-shirts); Latinos (with a line of products including clothing and buttons); and young mothers (including a $20 “Babies for Obama” onesie).

The categories expand on Obama’s efforts in 2008, which pushed the boundaries of political campaigns by aggressively marketing the candidate to groups within the disparate Democratic base. The segmenting underscores the importance that turnout is likely to play in the tightening race between Obama and Romney.

Neither the Obama nor Romney campaigns would discuss their micro-targeting activities or plans. Romney, who until this month was focused on winning the bitter GOP primaries, is expected to ramp up his targeting efforts in coming weeks.

Romney has already made fundraising appeals aimed at mothers after a Democratic strategist belittled Ann Romney’s stay-at-home-mom role. The Republican candidate’s campaign Web site offers $6 bumper stickers proclaiming that “Moms Drive the Economy.”

Celinda Lake, a Democratic pollster, said micro-targeting is particularly useful when combined with Facebook, Twitter and other social media, encouraging like-minded supporters to recruit peers and help spread “viral” campaign messages.

“You can’t really target ‘swing voters’ on social media because nobody thinks of themselves that way,” Lake said. “This kind of micro-targeting is vital because it helps turn people from passive, captured audiences to identified, active participants.”

But strategists in both parties warn that the approach has limits. Peter Daou, a digital media strategist who worked for John F. Kerry’s and Hillary Rodham Clinton’s Democratic presidential campaigns, said there’s a danger of losing sight of the broader themes and voter-organizing efforts needed to win elections.

“Some of this can be taken a little too far, because the macro environment is always going to override the narrow interests of various voters,” Daou said. “Once you’re getting down to pet lovers, I have a feeling that the bigger issues will override any of the work you do there. It can help on the margins, but that’s about it.”

Some of the pitfalls are clear on the Pet Lovers for Obama Facebook page, a mostly fluffy affair featuring dozens of photographs of dogs, cats and at least one goat wearing pro-Obama swag.

But the page also has its share of detractors, including those urging animal lovers to vote against Obama, and recurring lists of dog-eating and dog-on-car jokes. “Oh my God, just when I thought people couldn’t be more shallow and lame, this pops up,” one user wrote in a recent comment, adding that Obama is “the worst president ever.”

Another called the page “ridiculous.” “What next,” they asked. “Starlings for Obama . . . ?”