WASHINGTON — President Barack Obama’s campaign raised more than $70 million combined for his re-election and the Democratic party during the summer, an amount that gives him a clear advantage over his Republican rivals but is less than his initial fundraising effort.

The fundraising total announced this morning exceeds a goal set by the campaign of $55 million combined for the July-September fundraising period but is about $16 million less than Obama raised during the April-June quarter.

Obama has dealt with declining poll numbers and a weakened economy during the summer, prompting the president to recently call himself the “underdog” in the presidential race.

Campaign officials had said they would raise less because of canceled fundraisers during the summer’s debt ceiling negotiations and a typical summertime lull in raising cash.

Obama campaign manager Jim Messina said in an e-mail to supporters that more than 600,000 people donated to the campaign in the most recent quarter. He said more than 980,000 people have given money to the campaign.