President Obama is turning 51 on Saturday, with just three months until Election Day. So he will celebrate in true political fashion: spending “downtime,” as an e-mail invitation put it, at a party at his Chicago home with a bunch of strangers who made campaign donations to be there.

That party, on Aug. 12, will mark another milestone in the transformation of the president and his wife, who once tried to limit the role of politics in their lives and now seem to be increasingly giving themselves over to it. Even some longtime Obama fund-raisers expressed surprise over the party’s site: the Obamas have limited their schmoozing hours in Washington, sequester themselves while on vacation and seldom invite many outsiders into the White House living quarters. Until now, they have kept their Chicago home mostly sacrosanct, allowing only limited photographs of the interior.

The party raises questions about how far the Obamas will go in mortgaging their personal appeal for political gain in the months ahead. In poll after poll, voters give Mr. Obama higher marks as a person — a trustworthy leader, a committed father — than as a steward of the economy. Aside from their house, how much of themselves are the Obamas willing to offer up?

Consider the shift in Mr. Obama’s birthday celebrations since he arrived in office in 2009. That year, with re-election still distant, Michelle Obama gave him an entirely private surprise party at Camp David, Md., with a few old friends. His 2010 party was splashier, a basketball tournament that made news because of the professional and college stars who played.