(John Kemp is a Reuters market analyst. The views expressed are his own)
LONDON, Nov 8 (Reuters) - American opinion on hydraulic fracturing appears to be dividing along partisan lines, with Democrats opposed even in areas where there is little drilling, while Republicans are far more likely to be in favour.
In elections on Tuesday, voters in three Colorado cities supported ballot measures prohibiting hydraulic fracturing or imposing a moratorium for five years.
The fate of a similar initiative in a fourth city hangs in the balance, pending a recount, with supporters of a moratorium trailing by just 13 votes out of more than 20,000 cast.
The Denver Post, the largest-circulation local newspaper in the state, and a supporter of oil and gas development, called the fracking bans "regrettable."
"After grinding the Keystone Pipeline to a halt, it's clear that activists have zeroed in on their next target, and are influencing the conversation with stunning effect," wrote Forbes magazine, which called the votes "ground zero in the hydraulic fracturing debate."
Colorado is a crucial battleground for supporters and opponents of oil and gas production through hydraulic fracturing.
The state contains all or part of seven of the 30 largest gas fields in the country, according to the state geological survey.
Colorado is the ninth-largest oil producer in the country, and thanks to hydraulic fracturing production is growing faster than almost anywhere else outside Texas and North Dakota.
In the first week of November, 70 rigs were drilling for oil or gas in the state, ranking it fourth in terms of drilling activity behind Texas (817), Oklahoma (176) and North Dakota (163).
Drilling is targeting Colorado's part of the Niobrara shale formation which lies under most of the northern part of the state.
By late 2010, more than 900 oil wells had been drilled into the Niobrara, almost all of them in Weld County, and 15,000 gas wells were producing from the same formation, most in Weld and Yuma counties, according to state geologists ("Colorado's New Oil Boom" Spring 2011).
Just two counties, Weld and Garfield, account for over 60 percent of all the active oil and gas wells in the state, and are still the main targets for new drilling.
Out of a state-wide total of 3,345 new applications for permission to drill approved so far in 2013, 2,048 were in Weld and 691 in Garfield, accounting for 82 percent of the total, according to the Oil and Gas Conservation Commission, which regulates the industry.
FRACKING FAULT LINE
The four cities that voted on bans or moratoriums all neighbour Weld. But none is currently a significant oil and gas producer.
The cities of Boulder and Lafayette voted for a five-year moratorium on all new exploration and development activity. But Boulder County, in which both are located, has just 321 wells (less than 1 percent of all those in the state). Only 22 drilling permits were approved in 2012 and none so far in 2013.
Fort Collins, in Larimer County, voted for a fracking moratorium. But the county hosts only 254 wells and just 13 applications have been granted since the start of 2012.
The City and County of Broomfield, where supporters of fracking are ahead by just 13 votes pending a recount, has fewer than 100 wells, and fewer than 40 applications in the last two years.
Governor John Hickenloooper, a Democrat who trained as a geologist and began work in the petroleum industry, is backing a lawsuit by the Colorado Oil and Gas Association to overturn an earlier fracking ban approved by another small municipality in the state.
Colorado is something of a bellwether state. Historically a Republican stronghold, it has become a swing state following an influx of Democrats into urban areas such as Denver and Boulder.
According to state records, one third of voters are registered as Democrats, one third as Republicans, and one third as unaffiliated with any party.
Coloradans backed George W. Bush for president in 2000 and 2004 and Barack Obama in 2008 and 2012, but in each case the winner's margin was among the closest nationally.
The state's congressional delegation is split between five Democrats (both senators and three representatives) and four Republicans.
However, in Boulder, registered Democrats outnumber Republicans by more than 2:1. Larimer is a Republican-leaning county, but the college town of Fort Collins leans Democrat.
Broomfield, which split down the middle over fracking, is also almost evenly divided between voters registered with the two major political parties.
Oil and gas-producing Weld, by contrast, is dominated by Republicans and independents.
The state shows a sharp partisan divide. Boulder and Denver counties contain 27 percent of all registered Democrats, but less than 10 percent of the state's registered Republicans.
That split is now replicated in attitudes towards fracking, and oil and gas development more generally.
Petroleum-producing counties, such as Weld, Garfield, Moffat, Rio Blanco, Jackson, and Yuma, all lean Republican, and remain open to fracking. The state's Democratic areas, none of which is a major site for drilling, increasingly oppose fracking.
In Colorado, as in many other areas of the country, local attitudes towards hydraulic fracturing are dividing along ideological lines as well as being shaped by familiarity with oil and gas production.
(Editing by Anthony Barker)