President Obama has the star power to raise millions of dollars for the candidates and organizations he graces with his stump speech. 

But when the president hit the road Tuesday for a two-day fundraising tour to pack the party coffers, he also was racking up a $265,000 partisan bill for just one leg of the trip, according to a watchdog group -- part of which taxpayers, regardless of party affiliation, will have to pay. 

Obama started out in Las Vegas, where he stumped that night for state Democrats and Senate Majority Leader Harry Reid. On Wednesday night he was to attend a two-tiered donor dinner for the Democratic Party in Los Angeles.

But sandwiched between political appearances, Obama squeezed in some quick public remarks on energy, ironically before burning fuel to Los Angeles, at Nevada's Nellis Air Force Base. It was a key stop, because it gives the entire trip an air of official legitimacy and allows the White House to write off part of the trip under rules governing travel, said Pete Sepp, vice president for policy and communications at the National Taxpayers Union. 

"You've got to have some official (business) in the trip somewhere. It becomes almost a game to find some official function to hang the trip on," Sepp said. 

The rest, though, is all politics. And, if history is any gauge, the American taxpayer will pick up a large portion of the tab. 

Sepp estimated that the purely political part of the trip -- the distance from Las Vegas to Los Angeles and back, with no public events -- would cost at least $265,000, just for air travel expenses. 

He said the minimum domestic travel package for the president consists of one Boeing 747, which serves as Air Force One, one back-up dummy plane and one C17 cargo plane. The cost estimate is based on past hourly operational costs for the three aircraft, adjusted for inflation. 

White House travel rules, which were developed under the Reagan administration, state that the Air Force pays all costs for the use of the aircraft, but that the government must be reimbursed for airfare, food, lodging and other expenses incurred during whatever portion of the trip is political. 

White House spokesman Tommy Vietor said the Democratic National Committee is paying its share for this trip. 

"The DNC is paying 100 percent of the legally mandated costs for the trip from Nevada to California, and we are complying fully with all legal requirements," Vietor wrote in an e-mail to FOXNews.com. 

But reimbursement for political activities involves a tricky formula, and actual reimbursements typically come nowhere close to compensating the government for the cost of such trips. Secret Service costs, for one, are always footed by the government. 

A 2006 report for the House Committee on Oversight and Government Reform found that during 2002, political campaigns reimbursed the federal government for $198,000 of the $6.5 million in flight expenses racked up by campaign-related stops made by President George W. Bush and Vice President Dick Cheney. That's 3 percent of the total cost. 

Taxpayers paid the remaining $6.3 million. 

"The president and vice president can legally participate in campaign and fundraising events for candidates," the report said. "But when they do so, the taxpayer bears most of the cost." 

That Obama is raising funds while in office is hardly unusual. Both Bush and Bill Clinton made similar political trips in their presidencies. 

Watchdog groups don't suggest that the president shouldn't travel, or even that the president should not travel to political events. Rather, they say the White House should be more forthcoming with its travel expenses and details and establish a more equitable reimbursement program. 

"You can't keep the president from traveling. That's what he does. ... No one would suggest he not travel," said Leslie Paige, media director for Citizens Against Government Waste. "What is most important for taxpayers is how much is it costing for this stuff." 

"Having more realistic reimbursement rules for political legs of these trips would be quite helpful," Sepp said. 

Paige said more transparency is needed, noting it's "very hard" to pry the full costs of these trips from any administration. 

The DNC did not respond to a request for comment; Sepp said any DNC reimbursement for Obama's trip this week would be minimal.