Washington ? Headlines in 1928 asking “Is Hoover Human?” prompted presidential candidate Herbert Hoover to take drastic steps to present a more empathetic image as the Great Depression settled over the nation. He trotted out his dog.

Photos of a smiling Hoover with King Tut, his Belgian police dog, started appearing in newspapers across the country, showing the remote president to be a regular guy. Sort of.

It is not the only time in presidential history that a pet has been brought in to bolster sagging polls. An exhibition unveiled last week at the White House Visitor Center follows a parade of White House animals-in-residence.

“Pets have provided great public relations for presidents,” said Katie Marages Schank, who helped organize the show for the White House Historical Association and the White House Curator’s Office. “Pets are used for political purposes, philanthropic purposes, photo ops, companionship and paparazzi fodder.”

Fifty photographs, many never published, were culled from presidential libraries, the Library of Congress, the White House Historical Association and the White House Photo Office.

“If you want a friend in Washington, get a dog,” Harry Truman so famously said. Truman’s public approval ratings were among the lowest of any presidency. He got two dogs, Mike and Feller.

Richard Nixon’s cocker spaniel, Checkers, is remembered by many as a presidential dog, though he never lived at the White House. He was the family dog before Nixon was elected vice president in 1952. Nixon’s presidency featured a gray French poodle named Vicky, plus a Yorkshire terrier and an Irish setter.

Franklin D. Roosevelt’s Scottish terrier named Fala has gone down in history as one of the most beloved White House pets. “Roosevelt spoiled him and took him everywhere. He would sit in on meetings with Winston Churchill,” Schank said. As part of the war effort in 1942, it was announced that Fala had given up his rubber bones to promote scrap collection. The dog attended FDR’s funeral in 1945.

Occasionally pet PR has backfired. After Lyndon Johnson lifted his beagle Him by the ears in front of the press corps in 1964, a barrage of furious letters poured in about animal mistreatment.

Schank said the White House always gets tons of mail – good and bad – about presidential pets. “It’s a way for people to relate to the president. They see a president who has the weight of the world on his shoulders, and he’s out throwing a tennis ball on the lawn with his dog,” she said.

Dogs are the clear presidential pet of choice. Bill Clinton was looked upon suspiciously by some for owning only a cat, the black-and-white Socks. “Articles asked, ‘Can you trust a man who has a cat?’ People think they are sneaky,” Schank said. “A dog is viewed as solid, a trustworthy companion.” Clinton later got a chocolate Lab named Buddy in 1997.

In recent administrations, pets have gone multimedia. English springer spaniel Millie “dictated” a book to First Lady Barbara Bush that raised $900,000 for charity. Barney, the Scottish terrier who was a gift to President and Laura Bush from then-New Jersey Gov. Christine Todd Whitman, prompted the online Barney Cam. The dog “has really taken advantage of the Internet as a form of communication,” Schank said.

So far no pet has emerged from the crowd of 2008 presidential candidates, though most have cats or dogs. “As far as I know, Barack Obama is petless, and so is Chris Dodd,” Schank told a crowd at the exhibit opening.

Those two might want to heed the words of Calvin Coolidge, owner of an elegant white collie named Rob Roy: “Any man who does not like dogs and want them about does not deserve to be in the White House.” Let us assume he would say the same of a woman.

“White House Pets” will be on display through March 9 at the White House Visitor Center, 1450 Pennsylvania Ave.