For all Senator Barack Obama’s success at raising money and generating excitement among voters, he faces a daunting challenge as he prepares to claim the nomination in August: a Democratic convention effort marred by costly setbacks and embarrassing delays.

With the Denver convention less than two months away, problems range from the serious  upwardly spiraling costs on key contracts still being negotiated  to the mundane, like the reluctance of local caterers to participate because of stringent rules on what delegates will be eating, down to the color of the food. At last count, plans to renovate the inside of the Pepsi Center for the Democrats are $6 million over budget, which may force convention planners to scale back on their original design or increase their fund-raising goals.

The convention is being organized by the Democratic National Committee, which is run by Howard Dean, with his chief of staff, the Rev. Leah D. Daughtry, leading the effort. Only in the last month has the Obama campaign been able to take over management of the convention planning with the candidate claiming the nomination, and his aides are increasingly frustrated, as the event nears, at organizers who they believe spent too freely, planned too slowly and underestimated actual costs.

The Obama campaign has dispatched 10 people to Denver to help “get a handle on the budget and make hard decisions” about what has to be done and how to move forward, said Bill Burton, a campaign spokesman.