Americans for Prosperity, the Tea Party-aligned group part-funded by the billionaire Koch brothers, is building a state-of-the-art digital ground operation in Ohio and other vital battleground states to spread its anti-Obama message to voters who could decide the outcome of the presidential election.

The group hopes that by creating a local army of activists equipped with sophisticated online micro-targeting tools it will increase its impact on moderate voters, nudging them towards a staunchly conservative position opposed to President Obama's economic and healthcare policies. Americans for Prosperity (AFP) is spending tens of millions of dollars developing its local strategy, already employing more than 200 permanent staff in 32 states.

Classified a non-profit "social welfare" organisation, AFP is legally obliged to project itself as a non-partisan campaign that neither endorses nor opposes candidates for public office. But there is no disguising its targets, nor their political nature.

In Ohio, volunteers are given a script which they follow when engaging voters. "President Obama took office three years ago and promised to fix our economy," they say, "yet unemployment is still high and our debt is up to $6tn."

AFP has already spent $30m so far this election cycle in opposing President Obama and other prominent Democratic candidates and their policies. It says it aims to reach up to 9 million targeted voters in crucial swing states, through the efforts of its 2 million activists.

But it is ambitions do not stop on election day on 6 November. "The goal is to build a long-term grassroots infrastructure," its president, Tim Phillips, told the Guardian. "We are not some election-year group desperately trying to ramp up attention – we are in this year-in year-out to make a difference in favour of economic freedom."

AFP's growing influence is highly visible in Ohio, one of the most crucial battleground states upon which November's outcome depends. It now has 80 paid staff operating in the state out of seven permanent offices.

Volunteers are empowered with mobile canvassing technology that directs them to the households that are most likely to be influenced by AFP's message of small government and tax cuts through software built on to handheld tablet computers. They are also equipped with the latest phone banking technology through which they have made 400,000 calls to Ohio's voters since May.

AFP's funding status allows it to raise unlimited sums from undisclosed sources, among them David and Charles Koch, brothers whose oil, coal and plastics businesses have earned them personal wealth of $25bn each. David Koch is president of the organisation's foundation.

Research by the independent Wesleyan Media Project has found that AFP is spending an astonishing $6m every two weeks on TV advertising that favours Mitt Romney's presidential candidacy. That pays for more than 7,000 TV ads to be served in the battleground states and outguns even Romney's own spending on political adverts.

With the presidential race tightening across the country in the wake of Obama's widely denounced performance in the first TV debate earlier this month, all eyes have turned to Ohio, which Romney must win if he is to have a fighting chance of taking the White House. No Republican candidate in history has won the presidency without bagging Ohio's electoral college votes that today stand at 18 out of the 270 needed for victory.

Polls vary widely in Ohio, making predictions difficult. But the latest tracking survey by Real Clear Politics has Obama two points ahead of Romney – a statistical tie.

AFP is also waging an aggressive campaign against Sherrod Brown, the Democratic senator for Ohio, under the rubric: "Has Brown worked for you?" It has a fleet of vans bearing the senator's picture with the logo: "Obama's rubber stamp for failure."

Leading figures within the Ohio Democratic party have been watching the activities of AFP and other outlying conservative groups with mounting alarm. Ted Strickland, the former Democratic governor of Ohio, told the Guardian that in his view the activities of such groups had the capacity "to move us from a democracy to an oligarchy where a handful of wealthy people use their money to try to control the political process".

Strickland said that Brown's struggle to get re-elected was a "clear example of the corrosive influence of outside money. He should be 20 points ahead were it not for a massive amount of negative advertising coming from billionaires trying to buy a senate seat".

(Recent polls have put Brown and his Republican challenger, Josh Mandel, neck and neck, though the latest survey from the Columbus Dispatch shows the incumbent pulling ahead.)

AFP's ground operation in Ohio and other states is built around an interactive online network that links its volunteers with a centralised database of information on millions of American voters. The database, called Themis after the Greek god of wisdom, was created with the help of seed money from the Kochs.

The database draws information on voters from a range of public and commercial sources to create a profile of their likely political behaviour. What you buy on Amazon; the magazines your subscribe to; your friends on Facebook; your age, neighbourhood, occupation and house value; what petitions you have signed; what church you belong to; whether or not you own a gun – all such data points and many more go towards the creation of your personal, albeit anonymous, voter file.

That, in turn, allows AFP activists to micro-target households with a level of precision that could only be dreamed about in previous generations. "This is an exponential leap forward for our side – with Themis as our crucial partner, we are able to leverage our dollars and refine our message," Phillips said.

Much media attention has been paid this election cycle to the avalanche of billionaires' money, including that of the Koch brothers, that has been spent on negative TV adverts. But in the longer term, the creation of this local lattice of activists able to identify key voters through online micro-targeting could prove to be a far more effective political weapon.

In AFP's case, its interactive database serves up what the group calls an "affinity score" for each voter. He or she is awarded a number from 0 to 1. Those registering 0 on the scale being so leftwing and pro-government in outlook that, from the organisation's perspective, they are not worth bothering with.

Those showing a 1 are equally worth bypassing because they are already so in favour of tax and spending cuts that to talk to them would be preaching to the converted. The technology is interactive, so that if a volunteer discovers that the affinity score of a voter on the doorstep is inaccurate – he or she is found to be more or less fiscally conservative than the rating suggests – it can be instantly corrected. The information is sent back at the push of a button to Themis, which is thus constantly updated and improved.

The target group for AFP are those voters who fall between 0.4 and 0.6 on the affinity score – those moderate voters deemed by its digital planners to be "persuadables". "Our goal is to get everybody into the 0.7 to 1 zone. We want to move the center towards economic freedom, to drive the debate through word-of-mouth marketing," says Matt Seaholm, the national field director of AFP.

He added that in his view it was working; that AFP were driving the debate to the right. "Cap-in-trade is now a dirty word. Stimulus is now a dirty word. Debt and spending are at the forefront. These were things that were not talked about in the past."

AFP began testing its new micro-targeting gadgetry in Wisconsin last year, where it used the technology to energise its 120,000 activists in a succession of volatile recall elections. The group's efforts were one factor behind the survival of the Tea Party-backed governor, Scott Walker, in his recall vote this June.

Phillips rejects the argument that AFP and other conservative outside groups are having a pernicious impact on the democratic process. "We are proud to have the support of the Kochs. They have every right to be involved in the political process – they have been steadfast in this area for four decades."

He added that for Obama and other Democrats to complain about corporate money entering politics was "hypocrisy at its greatest. It's laughable, and most Americans know it. Obama receives tens of millions from Hollywood and the entertainment industry – so that is good money, and other money is bad?"