ATTEND a Democratic campaign event, trawl left-leaning websites, speak to a candidate or activist, and conversation quickly turns to the right’s billion-dollar plot to buy November’s elections. Thanks to the Supreme Court’s ruling in 2010 in Citizens United, companies (and unions) can now donate without limit to “super PACs”, which are free to spend as much as they want advocating the election or defeat of particular candidates. As a result, the complaint runs, conservative groups will have enough money to flood the airwaves with attack ads, drowning out more representative voices and creating an artificial Republican tide.

The staff of the most prominent such outfit, American Crossroads, which was founded by Karl Rove, the mastermind of George W. Bush’s two victorious presidential runs, do not describe things very differently. Yes, thanks to their efforts, as well as the counter-arguments from the other side, the airwaves in swing states will inevitably be saturated with political advertising over the next two months. Yes, right-leaning groups will probably spend close to $1 billion in an effort to install a Republican president and Congress. The main disagreement between practitioners and critics of unlimited “outside spending” is more basic: the practitioners sound far less certain that a record-breaking advertising blitz will be enough to unseat a sitting president.

It was actually Democrats who proved how little electoral success an abundance of riches could buy in 2004, when left-leaning 527s (a sort of precursor to super PACs) spent almost twice as much as right-leaning ones without toppling Mr Bush. In part, that was because the Republicans who were out to besmirch John Kerry were so good at it that they more than compensated for their relative penury. Mr Kerry wanted to run as a war hero who understood how best to defuse the various conflicts Mr Bush had rushed into. But conservative 527s such as “Swift Boat Veterans for Truth” managed to paint him as a cowardly fraud unworthy of the medals he had won, before his campaign had had a chance to disseminate its version of events. Republicans also proved better at getting their supporters to the polls. Result: a relatively unpopular incumbent squeezed back in.

The Obama campaign seems to be banking on a similar outcome this year. It claims its massive investment in grassroots outreach will shield it against the expected pyroclastic flow of negative advertising. Meanwhile it and Priorities USA Action, a super PAC in Mr Obama’s corner, have tried to get their character-assassination attempt in early, before the autumn rush. They have spent the summer—and a good deal of money—depicting Mitt Romney as a blood-sucking corporate parasite. The goal is to undermine his chief selling point, that a successful businessman may understand best how to get the economy moving.

Not only has the Obama campaign outspent Mr Romney’s on the airwaves over the past few months, media types say, but it has done so with sophistication. It makes its Spanish-language ads from scratch, for example, rather than just recording a new voice-over for an existing English ad, as Mr Romney’s campaign sometimes does. It has been airing ads in small towns in safe Republican states, such as Dothan, Alabama and Parkersburg, West Virginia, merely to reach little pockets of voters in neighbouring swing states. It is also much more of a presence on the radio.

It has fallen to American Crossroads, its close relative Crossroads GPS (which, unlike the super PAC, does not have to disclose its donors but has to dress up its electioneering as a campaign for “social welfare”) and other conservative groups to fight back. And they have: the Crossroads groups plan to spend $240m-300m on this election. Others, including the Chamber of Commerce, Americans for Prosperity and a super PAC backing Mr Romney are also planning big outlays. So far, such outfits on the right have spent roughly $200m to the left’s $50m.

All this has more than compensated for the Romney campaign’s relatively modest investment in advertising so far, according to Elizabeth Wilner of Kantar Media, a firm that tracks such things. The Republican outside groups are on the air in all the markets where the Obama campaign is, and then some. Ms Wilner fully expects the weight of advertising to shift even more decisively in the right’s favour as the campaign wears on.

A hard man to smear

But it is hard to change voters’ views of an incumbent, after four years in which they have been building up firm impressions of their own. Worse, says Steven Law, the president of both American Crossroads and Crossroads GPS, Mr Obama is a particularly tricky man to tear down. Voters are well disposed towards him. They bridle at attempts to label him a liberal and recoil when he is mocked or attacked too aggressively, perhaps because of his status as the first black president. A tone of regret and disappointment, rather than anger or indignation, is imperative.

Mr Rove understands this. One of Crossroads’ ads features a woman explaining how she voted for Mr Obama in 2008—“He spoke so beautifully”—but now agonises about her family’s finances and the national debt. In another a female voice says, “He raised our hopes. He seemed to understand. But today he’s different.” In a third, yet another middle-aged woman with children (spot the swing voter) laments, “He promised change. But things have changed for the worse.”

Making any sort of impression on voters will become harder as the advertising firestorm reaches its full intensity in September and October. Outside groups might even have to resort to (horrors!) some positive ads, simply to stand out, says Mr Law. The returns will inevitably diminish as the advertising tonnage increases, he concedes. But among pivotal groups in swing states in a close election, even diminished returns could prove decisive.

Economist.com/blogs/lexington