Colorado was until very recently a very reliable Republican state in Presidential elections. Even in 1996, the worst Republican Presidential year since Barry Goldwater, Bob Dole won Colorado despite the presence of Ross Perot on the ballot.

As with the other western battleground, Nevada, rapid population growth, particularly from Hispanics and West Coasters, has made the state competitive in a very short space of time. In particular, Colorado’s flourishing IT and electronics industies lured many young and well-educated Californians with the prospect of cheaper property, shorter commutes and beauiful scenery. Colorado, once part of New Spain, always had a significant Hispanic population (over 8% even in the 1940 census) which has been augmented by extraordinarily rapid immigration over the past 20 years. The Hispanic population of suburban Denver increased by over 50% between 2000 and 2010.

This is the land where South Park is set, and many locals have an appropriately sceptical attitude to both parties, with a definite tendency towards positions that produce large numbers of swing voters – socially liberal, pro-gun and economically moderate. The Centennial State has a particularly high number of voters registered as Independents. Significant liberal-left, socially conservative and economically libertarian blocs give both parties a firm base, but elections here are decided by the sceptical suburbanites in the middle.

Colorado is now a pivotal state in American Presidential elections. As befits that crucial role, Colorado played host to the most important moment of the 2012 Presidential campaign, the game changing first TV debate where Mitt Romney calmly tore apart an Obama/Axelrod playbook that had been working to perfection.

80% of Colorado’s population lives in the Front Range Urban Corridor, which follows both the eponymous chain of mountains and the I-25 Freeway for 180 miles from Fort Collins close to the Wyoming border, through Denver, to Pueblo down in the South. The Front Range is the first sudden eruption of the Rockies from the endless flatland, and its perfect combination of stunning scenery and excellent transportation links and are key to Colorado’s attraction for migrants.

Up in the north, Fort Collins, a university town and with a large element of both high-tech and old-school industry, is politically marginal with the academic element battling more conventional suburbia. The next major city along the freeway is Boulder, a very leftish university town that always produces big margins for Democrats of 2 or 3 to 1.

Metropolitan Denver is the key to any winning election in the Centennial State. Denver itself is a relatively small proportion of its metro area, casting 270k votes in 2008 to the 720k cast in the three bordering counties. Between them, these four counties cast over 40% of Colorado’s votes. Denver is racially diverse (31% Hispanic and 10% Black, the latter high by Western standards) and has a large population of well-educated, secular, singletons as well as a significant gay community. Needless to say, it is a Democratic stronghold, with the blue side winning round 70%

Denver’s sprawling, low-density, suburbs are where Colorado elections are really won – and lost – however. All of Colorado’s political and economic diversity is found among the endlessly sprawling cookie-cutter developments – NRA members and hippies, gay rights activists and conservative Evangelicals, marijuana dispensaries and megachurches, high-tech start ups and huge manufacturing plants. All of suburban Denver has a rapidly growing population, and especially a rapidly growing Hispanic population. Adams County has a definite Democratic lean, while Arapahoe and Jefferson Counties are swingier, won by Bush in 2004 but Obama in 2008. Working-class Jefferson, in particular, is seen as one of the most crucial battlegrounds in the nation.

Further south, the Republican votes really start piling up in the new exurban towns of Douglas County and especially around Colorado Springs in El Paso County. Between them, Douglas and El Paso produced a lead for George Bush of 125k in 2004, cancelling out a hair-line deficit of 25k in the rest of the state. Colorado Springs is famous as an epicentre of social conservatism, nicknamed the “Evangelical Vatican”, headquarters to Focus on the Family, the evangelical missionary HCJB shortwave radio station, and countless other parachurch organisations.

The southern end the endless sprawl of Front Range suburbia is marked by Pueblo, a heavily Hispanic and blue-collar city which along with Denver and Boulder is the third of the three real Democratic bastions in the state.

Outside the urban sprawl, the political picture remains complex. The eastern third of the state is High Plains country where corn and ranching are rule the roost. This area resembles, geographically and politically, the very conservative western regions of Kansas and Nebraska which it borders. Although sparsely populated, the Republican share of the vote here is exceptionally high, with even John McCain managing 80% in a few counties.

Southern Colorado, another sparsely populated agricultural area, votes Democratic, with demographics being the driver – once part of New Spain, a longstanding Spanish American population in the area has not only begun to lean more Demoratic in recent years, but the area has an exploding population of immigrants from Mexico and Central America working at low end agricultural jobs.

The western part of the state is known as the Western Slope, as it consists of the area west of the Continental Divide in the High Rockies, beyond which rivers flow into the Pacific rather than the Atlantic. This area is politically mixed, although as a generalisation the far west is heavily Republican, while the Intermountain region, in the state’s midwest, tends to be more mixed but definitely Democratic-leaning. Again, as a loose generalisation, the far west depends as much on agriculture, mining and gas as it does on tourism, whereas in the Intermountain region, tourism dominates the economy.

The largest city in western Colorado, Grand Junction, which unlike most gas industry centres has really struggled in recent years, sees big margins for Republican candidates and Romney may do even better than the historic trend. In the Intermountain region, upscale resorts like Aspen and Vail have a surfeit both of wealthy coastal liberals and struggling service staff, both demographics that Democrats do well among.

Colorado is peppered with military facilities, especially Air Force facilities including the headquarters of NORAD, and the uniformed and ex-uniformed vote is another big factor in Colorado politics.

Colorado has become a must-win state for both candidates. If Romney loses Ohio, and it seems more and more challenging for him, then he must win Colorado to stay in the race. For Obama, Colorado is a the key western flank of the much vaunted firewall, and its a part of the firewall now burned almost through to the last. RealClearPolitics.com currently has Obama in front, but only by a whisker of 1%. For much October, Romney was narrowly in the lead, but Obama seems to have rebounded in the past 10 days. This is a state that will go to the wire, and may yet prove as game changing on election night as it did on debate night.