WASHINGTON (AP) — President Barack Obama’s campaign expects to raise tens of millions of dollars less this summer than it did in the spring because negotiations over the U.S. debt limit forced Obama to cancel several fundraisers.

Obama’s campaign said Wednesday it canceled or postponed 10 fundraisers. Only weeks after the president’s campaign reported collecting a combined $86 million (€60 million) with the Democratic National Committee, Obama’s team is trying to lower expectations about its fundraising juggernaut while signaling to its army of volunteers and activists that they need to fill the void.

Obama is coming off a bruising battle with congressional Republicans over raising the government’s debt ceiling and is expected to face a formidable challenge from Republicans in 2012 against the backdrop of a weakened economy.

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Political fundraising operations typically slow down in the summer because many donors are on vacation and high-dollar events don’t usually resume until after Labor Day. During his first presidential campaign, Obama raised about $21 million in the summer of 2007, compared with about $33 million in the spring of that year.

Obama signed legislation on Tuesday to raise the debt limit and avoid a government default, but the negotiations kept him in the Washington area for the past month. Obama’s last fundraiser was in Philadelphia on June 30.

Obama is keeping his schedule on Wednesday, attending two fundraisers in Chicago to celebrate his 50th birthday, including a concert with Chicago natives Herbie Hancock and Jennifer Hudson and the Chicago rock band OK Go. Obama turns 50 on Thursday.

Republicans have accused the president of emphasizing campaign money over governing, criticizing plans for the lavish birthday party.

As part of Obama’s birthday events, Democratic officials and campaign aides are fanning out across the country for fundraisers.

Copyright 2011 The Associated Press.