WASHINGTON — President Obama walks into the Roosevelt Room of the White House and takes his seat around a table. The West Wing, as on most Sunday evenings, is quiet except for the tight circle of advisers who gather for a confidential briefing on his re-election. The gathering often takes place after Mr. Obama’s regular Sunday round of golf, and while the atmosphere is casual, the agenda is anything but: keeping the president immersed in what it will take to win a second term. He receives an update on how his operation is expanding in battleground states, he watches previews...