The candidates, who do a lot of talking about the need for greater energy efficiency, are not just asking who walks the walk but also, who drives the hybrid?
Democratic candidate John Edwards makes a point of telling people that after years of driving a regular sport utility vehicle, he and his wife bought a hybrid model to shuttle their kids, strollers, toys, luggage and other stuff between Washington, D.C., and North Carolina.
This month, Edwards announced his campaign would be "carbon-neutral," meaning it will do what it can to limit energy consumption and then buy "carbon offsets" to counterbalance the emissions produced by the energy it does use.
Edwards is not the only White House hopeful trying to make his own energy use part of the political equation this year.
Sen. Barack Obama, D-Ill., says he usually drives a flex-fuel vehicle, which can run on gasoline or a cleaner-burning blend of ethanol and gasoline. But he acknowledges that sometimes it is not practical to fill up with the ethanol blend, known as E85.
"My campaign leases a flex-fuel vehicle," he said in January, "but I'll be honest with you, a lot of times you're ... 30 miles from the closest E85 pump. It's going to cost you more to drive there and fill up than just filling up with regular gasoline."
Republican Mitt Romney, the son of a former Detroit auto executive, announced his candidacy while standing in front of a hybrid Ford Escape, which averages 36 miles per gallon in the city, and an old Rambler from American Motors Corp.
Romney said his father, George, who once headed AMC, championed the small, practical Rambler as "the first American car designed and marketed for economy and mileage. He dubbed it a compact car that would slay the gas-guzzling dinosaurs. It transformed the industry."
There still is plenty of transforming yet to be done, though - both nationally and by the politicians themselves.
Republican Rudolph Giuliani gave an energy policy speech in New York last summer that included a pitch for greater use of hybrid cars. Idling outside for him was a Cadillac Escalade. He did, however, opt to walk to his next destination rather than ride in the SUV, which averages 13 mpg according to the government's fuel economy guide. His campaign refused to say what he is driving these days.
Arizona Sen. John McCain, a Republican candidate for president, drives a Cadillac CTS, which gets city mileage in the 15-17 mpg range, the guide says.
Romney drives a 2005 Ford Mustang and his wife a Cadillac SRX SUV. The Mustang gets 17-19 mpg in city driving; an SRX about 16.
Romney campaign spokesman Kevin Madden said the campaign usually rents vehicles when on the road, adding that a flex-fuel vehicle was used on a recent swing through Iowa, where alternative fuels are popular.
Democratic candidate Bill Richardson, the New Mexico governor and former U.S. energy secretary, made a big show in 2005 of giving up his gas guzzling SUV Lincoln Navigator for a hybrid Escape, proclaiming, "I believe I should lead by example."
A few months later, the 6-foot-2 governor ditched the hybrid for a flex-fuel Chevy Tahoe LTZ after deciding the Escape was too small for him and his entourage, including a security detail.
"I can't fit in it," Richardson joked. "It goes about 20 mph." The Tahoe averages 11 mpg in the city when using the E85 blend, and 15 when running on gasoline.
Aides said that whenever possible, Richardson uses the cleaner-burning ethanol blend, which is known for getting fewer miles to the gallon but generating lower exhaust emissions.
Currently less than half of 1 percent of all gasoline stations offer E85.
Democrat Hillary Rodham Clinton, as former first lady, rides in vehicles owned and operated by the Secret Service. At the Clintons' request, the fleet includes a Ford hybrid, according to campaign spokesman Phil Singer.
Edwards, happy to promote his energy-efficient Escape, also still owns a 2004 Chrysler Pacifica midsize SUV and a 1994 GMC truck, according to state vehicle registration records.
Campaign spokeswoman Kate Bedingfield said the Edwardses, who have two small children, use the Pacifica when they need more than two seat belts in the back, and the truck when they need to move furniture or haul something.
Regardless of the candidates' personal vehicles, the whole adventure of running for president traditionally has been one colossal exercise in energy consumption, as candidates jet from state to state and then convoy from event to event in gas-hungry SUVS and vans.
The NRDC Action Fund, an affiliate of the Natural Resources Defense Council, estimates the leading candidates in the 2000 and 2004 presidential campaigns flew a million miles each.
The fund sent letters to 20 declared or potential candidates in February urging them to make this the first "carbon-neutral presidential campaign," by using hybrid or flex-vehicles, compact fluorescent light bulbs, recycling paper and materials and offsetting carbon dioxide emissions by purchasing credits, which are sold by those who have reduced their emissions of carbon dioxide.
NRDC spokeswoman Julia Bovey welcomed Edwards' announcement, saying, "Anyone running for president who claims they're going to be able to lead this country out of the energy and climate crisis needs to show they can do it in their campaign."
David Friedman, research director for the vehicles program at the Union of Concerned Scientists, declined to comment on the specific steps taken by the candidates.
But he said driving a hybrid vehicle can cut global warming pollution by about one-third compared with driving a nonhybrid of a similar model.
He said driving a flex-fuel vehicle, operating on ethanol made from corn, can reduce pollution by 10 percent to 30 percent. Also, carbon offsets, if properly verified and certified, can help support the use of renewable energy technologies that reduce pollution.