The job of surrogates is to make special-interest pleas, to do the partisan sniping that the candidates themselves might want to avoid, and to allow the candidates to spread their messages widely. And some indubitably have approval from the top to do just that. The omnipresent Bill Clinton has come to be known as Obama’s “surrogate-in-chief.” Likewise, when New Jersey Governor Chris Christie is tagged as a surrogate on talk-show appearances, surely the Romney campaign has given him the green light.

But what about people less likely to be working in concert with the candidates, but whose remarks the opposing campaign might simply like to pin on them? When Hilary Rosen, a lobbyist and Democratic pundit, said on CNN in April that Ann Romney “has never worked a day in her life,” the Romney campaign worked overtime to brand Rosen an Obama surrogate. Nothing would make Democrats happier, meanwhile, than to cast rocker Ted Nugent, who has used ultraviolent language in denouncing Obama, as a trusted Romney surrogate — as Democratic National Committee chairwoman Debbie Wasserman Schultz has described him. Los Angeles Times opinion writer Jon Healey took issue with that characterization. “Just because someone given to spewing cartoonish hatred endorses a candidate,” Healey wrote, “that doesn’t make him a ‘surrogate’ or a representative of any kind.”

Why are we calling people “surrogates” who in past years would have been known as “supporters”? It’s not just a change in label, after all: The words have fundamentally different roots and associations. And the shift from the straightforward “supporter” to the more loaded “surrogate” says a lot about how the political game has evolved.

The word “surrogate” has its roots in classical Latin: The verb surrogare or subrogare originally meant “to put in the place of someone else,” as when new elected officials were substituted for old ones. In the very first monolingual dictionary of English, Robert Cawdrey’s 1604 “A Table Alphabeticall,” “surrogate” is defined as “a deputy in another’s place.” But until recently, speaking out in favor of a candidate didn’t make you a surrogate: It made you an “advocate,” a “supporter,” a “partisan,” or a “booster.”

How did “surrogate” become, well, a surrogate for these other terms? We owe the word’s modern campaign usage to Richard Nixon, and, of all people, a talented wordsmith who worked for him: William Safire. “In the Nixon campaign of 1968,” Safire later wrote in his “On Language” column for The New York Times Magazine, “we were looking around for an important-sounding word for the person who was asked to stand in for the candidate on occasions not important enough for the presence of the candidate himself.” The staffers shot down various alternatives: “substitute was pejorative; pinch-hitter, too informal; stand-in, too theatrical. But surrogate sounded vaguely legal and dignified, and we went with it.”

An Aug. 17, 1968, article in The New York Times explained that “the ‘surrogate’ device is intended to take some of the crushing burden of campaigning off Mr. Nixon himself and permit him to concentrate on key states.” In a sense, having surrogates instead of plain old supporters meant a replicant-like power to be everywhere at once. And some of these body doubles would go on to their own starring roles. Among Nixon’s original surrogates were California Governor Ronald Reagan, Texas Congressman George H.W. Bush, and Illinois Congressman Donald Rumsfeld.