TUCSON, Arizona (Reuters) - A long-simmering movement by liberal stalwarts in southern Arizona to break away from the rest of the largely conservative state is at a boiling point as secession backers press to bring their longshot ambition to the forefront of Arizona politics.

A group of lawyers from the Democratic stronghold of Tucson and surrounding Pima County have launched a petition drive seeking support for a November 2012 ballot question on whether the 48th state should be divided in two.

The ultimate goal of the newly formed political action committee Start our State is to split Pima County off into what would become the nation's 51st state, tentatively dubbed Baja Arizona.

Backers have until July 5 next year to collect the 48,000 signatures required to qualify for a spot on the ballot. If they succeed, it would mark only the first hurdle in a long, circuitous process that even the most determined of supporters readily acknowledge has little chance of bearing fruit.

"We at least need to get it on the ballot, as a nonbinding resolution, to ask the people of Pima County if they want to be a part of Arizona," Tucson attorney Paul Eckerstrom, a former Pima County Democratic chairman who launched the campaign, told Reuters. "All the stars would have to align for this to happen, but it could conceivably happen by the fall of 2013."

U.S. history is replete with efforts to carve one state from another -- from the creation of Kentucky and Tennessee in the 1790s to more modern misfires like proposals to partition Long Island from New York or to split California in half.

The last successful intrastate secession movement was the formation of West Virginia during the Civil War.

SIZE MATTERS

Although Baja Arizona would be created from just a single county, it would hardly rank as the smallest territory to be granted statehood. Pima County exceeds Rhode Island, Delaware, Connecticut and New Jersey in land mass and surpasses several other states in population, including Alaska, Montana, Wyoming or the Dakotas, according to the U.S. Census.

Partisan tensions have long been a fact of life between left-leaning Pima County and a Phoenix-based political establishment that has produced such conservative giants as Barry Goldwater and John McCain.

But the rift was heightened during the past two years as Republican Governor Jan Brewer and her allies in control of the statehouse pursued a political agenda Democrats saw as extreme, including a crackdown on illegal immigration and proposals, ultimately unsuccessful, to nullify some federal laws.

State lawmaker Ted Vogt, a Republican who represents about one-fifth of Pima County residents, dismissed the breakaway movement as posturing by disgruntled Democrats who see themselves losing clout in state politics.

The county's three mostly rural, Republican-leaning House districts are growing, and so is their influence, Vogt said.

"I don't think a majority of Pima County residents want to leave Arizona," he told Reuters.

Even Tucson's best-known Democrat, Congresswoman Gabrielle Giffords, had to fight tooth and nail to fend of a Republican challenge in her bid for a third term in November.

The ballot measure sought by Arizona secession backers is a nonbinding measure asking Pima County voters if they support petitioning state lawmakers for permission to break away.

Before secession could occur, it would have to be approved separately by the Legislature, and by a second, binding referendum by residents of the proposed state.

If the Legislature refused, organizers could try to sidestep lawmakers with a statewide referendum. If both the Legislature and Pima County voters agreed, then it would be up to the U.S. Congress to grant Baja Arizona formal statehood.

The modern concept of Baja Arizona dates back to 1965, according to Hugh Holub, a local attorney widely credited with coining the term that year during anti-war protests at the University of Arizona. He supports the current effort.

"It sure sends a message to the rest of the world that we aren't like the folks in Maricopa (County)," he said, referring to the state's population center and capital.

But a more historical precedent can be found in Arizona's origins as a U.S. territory, more than half a century before statehood was granted in 1912. The northern bulk of Arizona was ceded by Mexico to the United States in 1848, six years before the lower portion of the territory, south of the Gila River, was separately acquired in 1854 under the Gadsden Purchase.

"It should have been its own state from the get-go," Holub said.

(Editing by Steve Gorman and Greg McCune)

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