(CNN) -- For all the headaches on the campaign trail, you would not think a candidate would be hounded by his own dog. 

That, however, has been the relentless fate of Republican contender Mitt Romney. A trip to Canada 30 years ago with the family pooch in a car top carrier, has been the gift that just keeps giving to Democrats. They've lampooned him as cruel at worst, foolish at best, with bumper stickers and T-shirts that say "Dogs aren't luggage!" and "Mitt is Mean!" 

Republicans have counterattacked by pointing out that President Obama wrote in his own book about eating dog as a child, helping the dog fight become a theme at this year's White House Correspondents Association dinner. 

Comedian Jimmy Kimmel nipped at both of them. "If Mitt Romney offers you a ride, call shotgun. And if President Obama starts buttering you, run!" 

It would be easy to dismiss all of this as political silliness were it not for one troubling fact: Sometimes the way a president connects with critters can affect the way voters relate to him. 

"Presidents and their pets have a long and storied history," says Garrett Graff, a goldfish owner and editor-in-chief at Washingtonian magazine. His theory about why voters take such an interest in such matters: "Most of us don't 'get' Middle East oil politics, and the rise and fall of the G.D.P., but we can 'get' if you connect with a dog or you connect with a cat." 

First a little history. Ever since George Washington took office with horses and hounds in tow, presidents have welcomed animals into their lives. A lot of animals. 
How long ago did someone go on a trip?
A trip to Canada 30 years ago