WASHINGTON — President Barack Obama flies Air Force One when he leaves town. So does Candidate Barack Obama.

Either way, taxpayers are on the hook for a hefty amount.

The souped-up Boeing 747 that typically serves as Air Force One costs $179,750 an hour to operate, according to the latest Pentagon calculations, meaning that expenses for presidential travel mount quickly.

And, no matter what the reason for the president’s trip, there are all sorts of other necessary big expenses anytime he moves around the country: advance teams, cargo planes, armored cars, Secret Service protection, communications and medical staff and more.

Presidents always are quick to stress that they reimburse the government for the costs of their political travel.

That’s true, but they do so under rules that still leave taxpayers paying most of the tab.

For political trips benefiting his own campaign, Obama’s team repays the government for air travel under a formula that’s based on what it would cost to charter a Boeing 737 for a comparable trip, according to the White House. Obama’s campaign doesn’t have to pay the full cost for a chartered plane, though. It pays a reduced amount based on the number of people aboard Air Force One who were traveling for political reasons. That number excludes Secret Service agents and other support staff who always travel with the president.

Obama’s political team also pays for items on the ground like food and lodging that are related to political events. Similar reimbursement rules govern political travel by the vice president and first lady, who fly on smaller, less costly military aircraft.

Despite the high costs to taxpayers, “these White Houses aren’t doing anything wrong,” says Brendan Doherty, an assistant professor at the U.S. Naval Academy who’s written a forthcoming book on presidential campaigning.

If a president had to pay the true costs of his campaign travel, says Doherty, he’d never go anywhere for political purposes.

Obama is the first president to pay for re-election travel under updated rules adopted by the Federal Election Commission in 2009 to implement a lobbying and ethics reform law passed by Congress in 2007.

David Mason, a former FEC chairman, said the new rules — linking reimbursement amounts to charter air rates rather than commercial airfare — require the Obama campaign to pay significantly more than it would have under the old rules.

When President George W. Bush was running for re-election in 2004, his campaign and the Republican Party reimbursed the White House more than $1.3 million for “airlift operations,” an Associated Press review of federal data shows. Those include itemized expenses for “in-flight services,” like food and catering, and the president’s helicopter, Marine One.

With the 2012 general election more than six months away, Obama already has exceeded that amount. Since late 2010, a separate Democratic Party “travel offset” account has paid roughly $1.5 million for similar expenses, according to FEC reports. And there can be considerable lag time between when political travel occurs and when reimbursements show up in campaign filings, so more payments are sure to be in the pipeline.

Even under the new rules, taxpayers end up paying a large share of the overall political travel costs for Obama, Mason said. He added that “it ought to be that way,” because of all the special costs related to presidential travel, including security and communications.

“Frankly, there are big advantages to being the incumbent candidate which I don’t think there’s a way to compensate for fully in the campaign finance regulations,” he said.

Since this is an election year, the party that’s out of power inevitably is sniping about taxpayer-subsidized political travel by the incumbent.

When Obama headed to Florida in early April for three private fundraisers and a half-hour “official” speech about tax fairness at Florida Atlantic University, for example, Republicans complained that he’d squeezed the school event into his schedule to help defray political costs.

But FEC rules specify that when there is any political activity at a particular stop, all travel to that destination must be reimbursed.

When a presidential trip includes multiple stops, some of them for political events and some for official purposes, then travel costs get divided up between the campaign and the government. But following a decades-old White House tradition, Obama aides declined to share details on how that’s done.

Asked about Obama’s reimbursements, White House spokesman Eric Schultz said the administration follows all federal rules governing reimbursements.

Meredith McGehee, policy director of the nonpartisan Campaign Legal Center, said the lack of transparency about how costs are divided up is troubling.

“It’s a pretty murky business,” she said. “Is the campaign paying its fair share? The answer is, we don’t know.”

Ari Fleischer, who was Bush’s White House press secretary, said presidents of both parties need leeway “to do normal things,” and that includes campaigning. They don’t have the option of traveling commercial or charter airlines, or losing the security and support entourage that always travels with a president.

But Fleischer said Obama seems to cross a line by striking an overtly political tone at non-campaign events, such as a recent speech in Florida on tax fairness and the socalled Buffett Rule, in which the president criticized the economic policies of some “members of Congress and some people who are running for a certain office right now, who shall not be named.”

Political rhetoric is in the ear of the beholder, however.

“I don’t think the president is doing anything that is out of the norm,” says Michael Feldman, who worked in the Clinton White House. “When he’s talking about the Buffett Rule, he is campaigning for a piece of legislation and an administration priority in his capacity as president.”

The Republican National Committee recently requested a Government Accountability Office investigation into what it said were campaign stops being passed off as “official events.”

Every recent president has faced finger-pointing over taxpayer-subsidized travel.

While the president’s ability to swoop in to political events on Air Force One is a huge advantage — and a bargain — for his campaign in many respects, it does come with a downside: It’s far easier for a challenger to hopscotch the country on a smaller plane and to quickly change plans as political dynamics shift. The high per-hour cost of Air Force One, for example, includes charges for fuel, supplies and short- and long-term maintenance for a plane unlike any other.

The cost breakdown for trips that involve a mix of political and official stops is particularly complex. And both Obama and his predecessor tended to mingle their fundraising with official travel, according to information compiled by CBS News’ Mark Knoller, who tracks presidential travel.

From the day he filed for re-election through April 9, Obama had taken 58 domestic trips, including 23 that involved political fundraising. Seventeen of those fundraising trips also included official events.

Whether a presidential event should be considered official or political is an unending source of controversy.

Kathryn Dunn Tenpas, who studied presidential travel for the Brookings Institution, said it’s difficult to draw a clear division.

“The office is inherently political,” she said. “I’m not sure how you would ever separate the political from the presidential.”