In the closing weeks of a closely fought presidential campaign, Mitt Romney will be mingling with wealthy Republican donors in Chicago, San Diego and San Francisco, hundreds of miles from the swing state voters who will make or break his White House bid.

President Obama will be traveling to New York, where the rapper Jay-Z will host a $40,000-a-head fund-raiser for him next week, and Los Angeles, where he is scheduled to raise a glass with the moneyed in early October, just days before the second presidential debate.

Say goodbye to the traditional fall fund-raising slowdown, when big-dollar bundlers could go back to their day jobs, major donors could put away their wallets and candidates could focus on shaking hands and kissing babies on the campaign trail. For the first time since the inception of public financing, each party’s candidate is declining the money for the general election.

Instead, betting that they can raise and spend far more on their own, Mr. Obama and Mr. Romney are committing to ambitious fund-raising schedules that are eating into valuable campaign time, tangling their travel schedules and complicating their efforts to woo voters.