WASHINGTON -- For sheer political opportunism, Hillary Rodham Clinton's got nothing on James Shields.

Footloose and eager to serve, Shields, the Irish-born nephew of an Ohio congressman, was Oregon's territorial governor in the mid-1800s. He later became a senator from Illinois, Minnesota and Missouri, moving to a new state each time he failed to gain re-election.

The "king of carpetbagging," one student of history has called him. Mrs. Clinton, currently pursuing a U.S. Senate seat in New York, might soon become the queen.

Even before she formally announces her candidacy, Republicans are pushing the issue every chance they get. "Hillary: Go Back to Arkansas, You Carpetbagger," read a protester's sign the other day in upstate New York, during Mrs. Clinton's 11th visit to the state this year.

Whether the carpetbagger label proves to be an insurmountable obstacle for Mrs. Clinton -- and some analysts think it won't be -- her Senate run virtually defines that term.

According to Safire's New Political Dictionary, a carpetbagger is "an outlander moving into a new area to seek political power at the expense of the native politicians." The first lady has already effectively muscled other Democrats out of her way, including the Bronx-born woman once considered the likely nominee, Rep. Nita M. Lowey, a Clinton loyalist with 25 years of bottom-up New York political experience.

For more than a century, politicians have tried to dodge the "carpetbagger" tag. But the earliest carpetbaggers were businessmen: frontier bankers who traveled light, lugging all their possessions in satchels made of carpet material. After the Civil War, "carpetbagger" became a Southern epithet for Northerners who invaded their devastated region to seek political office or a fast buck. Those who migrated south also included schoolmarms with more high-minded intentions: the enlightenment of Southerners of both races.

Mrs. Clinton, who grew up in a Chicago suburb, has never lived in New York. Her personal belongings could probably fit into the modern-day equivalent of a carpetbag -- a U-Haul van -- since she doesn't own a house or a car.

But it's an open question whether any of this will keep her from winning the seat of retiring Democratic Sen. Daniel Patrick Moynihan. Mrs. Clinton has already begun responding to her critics, arguing that "the kinds of issues that people in New York talk to me about are the kinds of issues that I have worked on for more than 30 years."

Her supporters are creating other lines of defense. They argue that New Yorkers have proved to be more tolerant of just this sort of thing. The Senate seat Mrs. Clinton hopes to fill used to be held by two men who had to fend off carpetbagger criticism: Robert F. Kennedy in 1964 and James L. Buckley in 1970.

Kennedy's campaign grew out of the assassination, a few months earlier, of his brother John. But it could not have happened if the Constitution did not provide that a House or Senate candidate need be a resident of the state only "when elected." (Running for governor of New York was out of the question, RFK's advisers discovered, because of the state's five-year residency requirement for that office.)

Kennedy was still registered to vote in Massachusetts on the day he won election in New York. Before he entered the race, his advisers took a poll and found that the carpetbagger label would not hurt too badly. But that didn't stop his political enemies from using it against him. (Kennedy lived briefly in the state as a youth but had no other New York connections.)

One joke that made the rounds at the time had Kennedy asking, "Where are the Bronx?" He managed to win, after trailing for much of the campaign, through the force of his personality. But other factors, including a massive Democratic vote in the presidential election, blunders by his opponent and residual affection for Camelot, also helped.

Buckley, who maintained a New York residence in addition to his longtime Connecticut estate, was elected to a single Senate term in 1970. He received only 38 percent of the vote but finished first in a three-way race.

After Moynihan unseated him in 1976, Buckley made a Senate try four years later in Connecticut, which, he insisted, was his true home state. He lost to Democrat Christopher J. Dodd, the son of one of the state's most popular politicians.

Analysts contend that the mobile society of the 20th century has made voters more tolerant of candidates who lack local links. Currently, 34 out of 100 senators were born in states other than those they represent.

Still, outsiders are often at a disadvantage in many parts of the country.

In Maryland, former Tennessee Sen. Bill Brock never managed to overcome the carpetbagger issue in his 1994 challenge to Sen. Paul S. Sarbanes, despite outspending the Democratic incumbent. Robert Kennedy's daughter, Kathleen Kennedy Townsend, got nowhere when she moved to the state in 1984 and two years later took on Rep. Helen Delich Bentley, a Republican, whose local ties stretched back over four decades.

Some believe that voters in large, cosmopolitan states with many transplanted residents, such as New York and California, are more open to outsiders.

"There are states and there are congressional districts where to be an outsider and not to have been born there or lived there would be an absolute handicap," says Richard Fenno, a University of Rochester political scientist. "I don't think New York is one of them."

New Yorkers' self-image may have something to do with it.

"Part of it is New York arrogance," says Maurice Carroll, director of the Quinnipiac College Polling Institute and a veteran observer of New York politics. "We're the capital of the universe. You want to be pope? Come on in."

That same attitude is less prevalent upstate, however, where resistance to Mrs. Clinton as an outsider might be higher and where the election could be decided. Carroll's surveys show that, statewide, roughly half of New York voters are bothered by Mrs. Clinton's nonresidency.

"This is an early issue. I don't think it has a lot of legs to it," says Fenno, the political scientist.