. . . “We have plenty of time for big rallies,” a campaign spokeswoman, Jen Psaki, said between the rallies on Thursday. “Our focus right now is on exciting our supporters and winning over undecided voters and the smaller and medium-size events are the best venue to accomplish that because the president can closely engage with the crowd.”

Big rallies are expensive, especially given the logistical and security challenges for a president as opposed to a mere United States senator. And Obama campaign operatives, both at the Chicago headquarters and in swing states where Mr. Obama recently has stumped, say the campaign intentionally limits crowds by restricting tickets. The reason is to allow the president to better connect with supporters, aides say.