Last week, we discovered that taxpayers footed a $225,000 bill for Hillary Clinton during her eight years in the Senate for the use of private jets for her travel. Today, National Review has an analysis of her 2008 campaign expenditures and discovers that her taste for luxury travel put a big dent in the pockets of contributors. In fact, while Mitt Romney traveled commercial during much of his runner-up effort for the 2008 nomination, Hillary spent much more on private jets than the man Democrats painted as too wealthy to connect to ordinary Americans — almost nine times more:

A deeper look into the candidates’ campaign expenditures reveals that Clinton spent more than nine times as much as Romney did on private jets during the 2008 race.

An analysis of public documents by National Review Online shows that Clinton took more than $19.2 million worth of private flights during the primaries before dropping out when then-senator Barack Obama finally built an insurmountable lead. Romney, who ultimately finished second in the primaries to Senator John McCain, spent just over $2.2 million on private-plane travel.

While Clinton’s longer campaign accounts for part of the disparity in private-plane costs — Romney withdrew in February 2008, four months before Clinton ended her run — Clinton had spent significantly more than Romney on chartered flights before the former Massachusetts governor dropped out of the race, too. By the time Romney called his campaign quits, the Clinton campaign had already spent $6.7 million on private planes — more than three times as much as Romney.

At first blush, this seems less of a big deal than Bloomberg’s scoop last week. Campaign contributions come voluntarily, after all, and with a specific purpose — to fund the candidate so that she can win an election. Travel expenses are a big part of that, but the manner of travel matters less than the end result, as long as no laws are broken. Hillary’s contributors probably wouldn’t have minded the private-jet travel in 2008 had she won the nomination and later the presidency. Even the loss probably matters more to them now than her wasting cash on private jets instead of commercial flights, although it might raise some questions as to whether some of that money could have been used better in the campaign.

However, it’s a pretty good marker to lay down now, especially for Republicans — and perhaps progressives, if Elizabeth Warren changes her mind and gets in the primary race. In 2008, Hillary stuck close to the establishment side of the Democratic Party, while Barack Obama won it on the basis of progressive populism combined with a veneer of post-partisan moralizing. Hillary will have to win the nomination in 2016 by indulging in the same progressive populism, which doesn’t really match up well with spending fortunes on private-jet travel paid for by the hoi polloi.

Those private-jet flights didn’t become an issue for Hillary in 2008, but Republicans seem intent on making them an issue in 2016. Don’t be surprised if any challenger from the progressive caucus within the Democratic Party doesn’t also make them a big deal, especially since at least some of that travel probably took place on corporate-owned or corporate-leased aircraft, as did the jets she used while in the Senate, and on the taxpayers’ dime.

However, CBS New York says that private-jet travel is no longer just for the wealthy. These days, anyone can afford it … assuming you’re flexible enough to take advantage of it:

Petrossov explains you have to be willing to fly at a moment’s notice to get the deal.

“Consumers can book it if they’re willing to adjust their schedules to last-minute demand,” he said.

For example, jets will fly customers paying full fares from Miami to New York. Next, that jet will have full fare customers waiting in Aspen and that plane may have to fly empty from New York to get them.

“Thirty percent of all jet flights are flying empty,” Petrossov said.

They will sell these so-called “empty legs” for just the cost of fuel, so booking that empty plane can cost a few hundred dollars, instead of thousands. But you have to be read to go when the opportunity is there.

In other words, travelers looking at this option have to have no commitments to destination, and no worries about adhering to a work schedule on either leg of their flight. That either requires one to be retired with plenty of cash, or independently wealthy — or just really, really lucky. Hillary’s already qualified on the first two, but we’ll see how far her luck holds out.

Update: Forgot to include the link to CBS New York. Fixed above.