OVER his second beer at The Shanty in Tucson, a pub popular among Democrats, Paul Eckerstrom gets to the point. “We don't like Phoenix,” he says of the state capital in Maricopa County to the north, home to more than half of Arizona's population. So Mr Eckerstrom, a lawyer and former chairman of the Pima County Democratic Party, has launched the long legal process to secede and form a new state, tentatively called Baja Arizona.

This idea of Baja Arizona is not new. Some trace it back to the Gadsden Purchase of 1854, when America bought from Mexico a strip of land south of the Gila river that was not included in the earlier cession after the Mexican-American war. More recently, the Midwestern snowbirds and others who flooded into Arizona mainly settled in Maricopa, making it politically dominant and distinct.

The differences start with the aesthetic. Middle-class houses in Phoenix tend to have lawns, whereas Tucson's mostly have desert landscaping, with artful cacti and such. Thomas Volgy, a politics professor at the University of Arizona and former mayor of Tucson, says that Maricopans want “to recreate Michigan”, whereas people in Pima accept that they live in a desert and use water responsibly.

Tucson is at heart a college town, the home of the state's flagship university. To the extent that intellectuals (such as Mr Volgy) moved to Arizona, they favoured Tucson. Pima County also has an old and rooted Hispanic community. By contrast, Maricopa is a largely white society with more recent Mexican immigrants. And whereas Maricopa is inland, Pima is on the border, which has always made its debate about immigration “more nuanced” than Maricopa's, according to Mr Volgy.

In Pima County and neighbouring Santa Cruz, this has led to moderate politics of a slightly Democratic hue, while Maricopa has become a Republican bastion. In the days of the Phoenix-born Barry Goldwater, Maricopa's conservatism was libertarian. But in recent years, as an ageing white population faces the increasingly brown young, it has turned nativist.

The epitome of this nativist turn is Joe Arpaio, Maricopa's sheriff (pictured right), who is notorious for his severity toward people he suspects of being illegal immigrants. By contrast, Mr Arpaio's counterpart in Pima County, Clarence Dupnik, though tough as nails, is seen as even-handed in his law enforcement, which makes him a lefty on Arizona's spectrum.

The career of Russell Pearce is another example. For many years Mr Pearce was one of Mr Arpaio's most enthusiastic deputies. Last year, as a Republican state senator, he sponsored SB1070, an anti-immigrant law so draconian that a federal judge promptly suspended parts of it. Mr Pearce has since become president of the state Senate and has followed up with a barrage of right-wing bills. One of these would have allowed Arizona to nullify federal laws it did not like.

The legislature last month voted against this package of bills after Arizona's business leaders, fearing for the state's reputation, lobbied against it. But to people like Mr Eckerstrom in Pima County, the mere attempt to pass a “nullification” law was too much to bear, suggesting that Maricopa, claiming to speak for Arizona, wants in effect to secede from America. Better, he thought, to secede instead from Maricopa.

There is another aspect to this story. It was in Tucson that Gabrielle Giffords and 18 other people were shot in January. Ms Giffords, a moderate Democratic congresswoman, also frequented The Shanty, and one of her campaign posters still hangs on the wall. Nobody there blames anyone but the gunman for the shooting. But people in Tucson saw it as a warning. Sheriff Dupnik called Arizona “the mecca for prejudice and bigotry”. In response to the shooting, the University of Arizona launched a National Institute for Civil Discourse. Its director says that Arizona has been “a test-bed for uncivil politics.”

Amid these sensibilities, the Maricopan extremism of Mr Pearce seems less tolerable. Many in Tucson roll their eyes when discussing the legislature's proposals to liberalise Arizona's gun laws, already lax, by allowing guns on university campuses.

So secession is tempting. Mr Eckerstrom cites Maine, which split from Massachusetts in 1820 after years of trying. And West Virginia seceded from Virginia in 1861, rather than join the Confederacy. Admittedly, most secession movements fail, and some are merely symbolic. Bits of Washington and Oregon have long talked about joining with British Columbia to form “Cascadia”. Texans talk about secession as Britons discuss the weather (endlessly, without doing anything about it).

The rift between Maricopa and Pima is different. Some compare it to that between Flanders and Wallonia in Belgium: complicated but real. The easy part will be collecting signatures in Pima County to place a non-binding initiative on local ballots in 2012. Other counties, such as neighbouring Santa Cruz, might do the same. The county governments would then ask the legislature in Phoenix to agree to the split, which Congress in Washington, DC, would need to ratify.

Mr Volgy, who has a faded “Baja Arizona” sticker from 1987 on his door, thinks the state legislature, dominated by Maricopans, might just let Baja go. “It used to be that we hated each other; now we hate them, and they ignore us,” he says. Either way, says Mr Eckerstrom, the message to Arizonans and others is clear: “Not everybody in this state is crazy.”