Robinson's family connection to Obama - the Democratic front-runner has been married to Robinson's sister, Michelle, since 1992 - makes him a natural for the role. He can speak about the candidate with a degree of personal knowledge and authority that few campaign surrogates can match.
And many of the skills Robinson has mastered as an Ivy League coach lend themselves to a political campaign, such as giving pep talks, recruiting, raising money and giving media interviews.
Obama is scheduled to make his first campaign appearance in the state on Saturday at a rally at Rhode Island College in Providence.
While he doesn't have an official role with the campaign, Robinson fields at least four interview requests a week and has appeared at events around the country when Obama can't make it. He's a frequent presence on TV and radio in Rhode Island, and has done everything from post-debate analysis to discussing what local venue might be big enough to accommodate a rally for his brother-in-law. He also encourages people to get out to vote and plugs the campaign's Web site.
At a February rally in Warwick, Robinson introduced his younger sister as the "next first lady" and reminisced about staying up late talking with her as kids in the bedroom they shared growing up on the south side of Chicago. The crowd cheered, then went wild as she came out and he gave her an extended hug.
Rhode Island votes Tuesday, and state officials predict a 30 percent turnout among the 660,000 registered voters, double the percentage that voted in the 2000 primary. Clinton held an edge in a Brown poll earlier this month and has the endorsement of Democratic Sen. Sheldon Whitehouse. Former Sen. Lincoln Chafee, a Republican-turned-independent, has backed Obama.
"When people get to know Barack, they'll make their own decision," Robinson said in an interview with The Associated Press. "I'm just trying to facilitate that, trying to convince people to take the time to get to know him."
Sports figures are popular, and people come to hear Robinson's stories, like the one he tells often about the first time he played basketball with Obama after his sister brought him home to meet the family. Robinson says he learned about Obama's character from his unselfish playing style - passing to his teammates, taking a shot when appropriate and not calling fouls unnecessarily.
"They are what they appear to be: regular folks trying to get something done the right way," he said of his sister and brother-in-law.
That personal connection to the candidate appears to resonate with voters.
"I think he really touches home about the reality of who these people are behind it all," said Kelly Taylor, a campaign volunteer who attended a fundraiser that Robinson headlined in Providence. "You're meeting someone who is giving you a window into the humanity behind all this, and I think it's very important what the character of our president is like."
Behind the scenes, Robinson has helped the campaign lock up money and endorsements. Jeffrey Padwa, Obama's campaign finance committee co-chair in Rhode Island, said he enjoyed hearing Robinson's basketball story, as well as how an already-ambitious Obama told Robinson soon after they met that he planned to run for office some day.
Coaches make natural advocates since they're used to selling their programs to recruits in the same way politicians sell their candidacies to voters, said Darrell West, a Brown political science professor.
"People want behind-the-scenes stories about what Barack Obama is like," West said. "A brother-in-law can help satisfy a public curiosity about who this guy is."
Earlier this month, before state Attorney General Patrick Lynch had publicly announced his endorsement, Robinson called him. Lynch, a former basketball star at Brown who helped screen Robinson for the coach's job, said Robinson's connection to Obama went a long way to winning his endorsement.
"He's real; he's not political," Lynch said of Robinson. "He's a tremendously effective surrogate."
Robinson also knows a great deal about what it takes to win. A former two-time Ivy League player of the year at Princeton, Robinson is trying to take the 15-9 Brown Bears to the school's first Ivy title in more than 20 years.
Robinson said he talks to Obama about once every two weeks, including after every big Brown game. Obama called in February after the Bears swept Penn and Princeton on the road for the first time in school history.
"I say to him, 'Keep up the good work, your job's way more important than this,"' Robinson said. "I'm humbled by the fact that he pays attention."