There were strings attached to the invitation to members of Congress and their families to last night's annual summer barbecue at the White House. Everyone was to join the First Couple earlier in the day at Fort McNair in Washington to stuff backpacks with books, Frisbees and trail mix for children of military personnel.
That the guests were expected to earn their supper – they called it a luau in deference to the President's Hawaii roots – was down less to the President than to his wife, who, five months after arriving at 1600 Pennsylvania Avenue, is trying to put a bolder imprint on the daily life there and not just in the social hosting and cultural departments.
A first sign that Mrs Obama was manoeuvring to step up her profile in the West Wing of the White House – where the President's staff toil and the real power resides – came earlier this month when she abruptly reshuffled her East Wing team. She said goodbye to her 37-year-old chief of staff, Jackie Norris, with whom she had apparently had some "wave-length" issues, and replaced her with 61-year-old Susan Sher.
Ms Sher, who was once Mrs Obama's boss at the Chicago Medical Centre, was chosen, according to people involved, in part because she was expected to be more forceful in ensuring that the First Lady was given a more substantive role on issues where she could actually make a difference. According to The Washington Post, the first thing Ms Sher told David Axelrod, political adviser to the President, upon taking the job, was: when I call, "you need to get back to me right away".
Encouraging volunteerism in America – like stuffing backpacks for children's summer camps – is one of the areas where Mrs Obama intends to make an impact. Earlier this week she travelled to San Francisco to launch a summer-long campaign to encourage volunteerism called United We Serve. She delivered a keynote speech at a convention on community service and visited a school project with Maria Shriver, wife of California's governor Arnold Schwarzenegger.
The First Lady's office has also made it clear that she is ready to play a significant part this summer (though she plans to take the month of August off from work) to help promote one of the keystone components of her husband's domestic political agenda: his plan for sweeping healthcare reform.
Mrs Obama is hardly the first presidential spouse to realise that her address and proximity to power gives her an unusual opportunity to make a difference wherever she chooses to focus. First among the activist first ladies was Eleanor Roosevelt, the wife of Franklin Roosevelt, who became a leading voice in the country for civil rights.
Hillary Clinton prompted something of a backlash for inserting herself too far into her husband's job, not least with the ambitious but doomed 1993 attempt at healthcare reform.
Mrs Obama has one very particular advantage at the moment: after some shaky weeks at the start of Barack's election campaign last year, she now enjoys solid, even remarkable, national popularity.
The high approval ratings – her success in matters of fashion and arm exposure may not have been unhelpful here – means that Mrs Obama will get attention whatever she does. But attention for the sake of it is not what matters to the First Lady, Ms Sher has said. "Whatever she talks about will bring press and interest, but it's important that she's not just talking but actually moving forward on those issues."
Also in the works: the hiring by Mrs Obama of her own speech-writer in the East Wing. "Her desire is to step out more and have deliverables," her communications chief Camille Johnston told The Washington Post. "It's about things that are coming up that we want to be a part of: child nutrition reauthorisation act, prevention and wellness for healthcare reform."
Mr Axelrod meanwhile admits that after five months of settling in and exploring the kinds of roles Mrs Obama could best play, some reassessment was inevitable. "We are focused now on quality events that are related to her passions," he said. "We don't want to use her as a utility player for political chores."
She may want to get more serious in her duties, but her playfulness has not deserted her. At Fort McNair Mrs Obama reassured everyone that the evening luau was going to be fun with "some great hula dancers". She then demonstrated some hula swaying, prompting Barack to playfully to say, "Try that again".