There's that often-repeated saying that Harry Truman made famous: "If you want a friend in Washington, get a dog."

Perhaps presidential candidate Senator Barack Obama is thinking ahead. He reportedly has promised his daughters that after the election this November, they'll get a family dog. That is, at least, what I've learned from the well regarded Best Friends Animal Sanctuary, which is also the nation's largest sanctuary for dogs. They've been circulating an email, which is being forwarded across the country, and was forwarded to me by a cousin of mine -- heck, maybe you've already read it -- that urges people to sign a petition asking Mr. Obama to get a dog from a shelter or a rescue group rather than a pet store.

As the Best Friends Animal Sanctuary explains, "With millions of homeless pets still being killed in shelters every year, please adopt your dog from a shelter or rescue group. Don't buy from a pet store or breeder."

They've gone as far as creating a web site, www.obamafamilydog.com, where they're asking people to sign this petition.On the other hand, if you're a lover of the pure breed, the American Kennel Club is asking the public "in the true spirit of doggy democracy" to vote online for what breed they think about best fit the Obama family. You can do that at www.presidentialpup.com.

Not that I want to take sides -- but if you're going to look at this from a financial standpoint, paws down, the shelter and rescue dogs win.

CostHelper.com has some great information on the cost of owning a dog in a typical year. They guess that you'll pay around $150 for a dog at a shelter or rescue center (and I'm guessing quite a bit less, especially when you get away from major downtown cities) and around $1,000 by going to a pet store or a breeder. Then, of course, if you have a puppy, you're going to spend money on shots and presumably getting your animal neutered or spayed.

They also mention that if you rent an apartment, you'll probably have to pay a pet deposit. Then again, you may want to pay for obedience school, or if you have a puppy that isn't housebroken, you may want to buy a cage for him to stay in when you're away. Or you could take my route and skip that and instead buy a new carpet and couch after your dog tears it apart...

My point is that there are a lot of expected and unexpected costs to having any pet, but particularly a dog. I haven't even mentioned dog food. So it seems to me that that's as good of an argument as any for going to a shelter or rescue group, though obviously someone who has a purebred dog might point out that they could breed their puppies or win competitions and make a small mint. But while you mull that over, voting for whatever type of dog you hope Barack Obama's family gets is free.

Geoff Williams is a business journalist and the author of C.C. Pyle's Amazing Foot Race: The True Story of the 1928 Coast-to-Coast Run Across America (Rodale).