Want to run for president? Get ready to spend.

President Barack Obama raised $59 million for his presidential campaign during the first half of 2007. To match that, prospective Republican challengers to his re-election would need to raise about $590,000 a day until June 30, if they entered the race today, Bloomberg reported.

Some experts are predicting that Obama could become the first billion-dollar candidate. “It would be extremely difficult, if not impossible, for the Republicans to raise as much money as Obama,” said former Republican National Committee finance chairman Al Hoffman Jr. in an interview with Bloomberg.

Republicans are gearing up, though. Independent outside groups, such as Karl Rove’s American Crossroads, are preparing for 2012. Prospective candidates are lining up major fund-raisers and preparing efforts to attract small donors.

Minnesota Gov. Tim Pawlenty said yesterday that he is setting up an exploratory committee to raise money for a possible candidacy.

Though many other likely candidates have yet to announce their candidacy, any serious candidate has already been laying the infrastructure that will allow him or her to raise money when needed, experts say.

Many also are following Obama’s example of focusing on small donors. Obama raised 54 percent of his money in contributions of $200 or less, according to the Center for Responsive Politics.