There are still 382 days before the Queen dissolves parliament, but Operation Get Farage is revving into action. Splashing allegations that he had a "mistress" across the Daily Mail and BBC news bulletins are being justified in the public interest, of course. The former Ukip MEP Nikki Sinclaire exploited the European parliament's immunity from libel law to throw the revelations to a slavering media pack. Farage was fuelling unemployment, she cheekily suggested, by employing both his wife and "former mistress Annabelle Fuller", a suggestion passionately contested by Farage and Fuller.

You don't have to be a fan of Nigel Farage to object to this style of politics. It's personal, lowest common denominator, play-the-man-not-the-ball nonsense, beloved by the likes of Tory spin doctor Lynton Crosby. By all means attack the hypocrisy of a party that rails against the "EU gravy train" while milking its expenses: in 2012, for example, Ukip MEPs claimed nearly £800,000 EU expenses and allowances. Opponents of the state often have the least scruples about taking from it, and given generous donations to the party from Ukip MEPs, it could be justifiably claimed that this virulently Eurosceptic-party is partly EU-funded. But let's not pretend this is anything other than an excuse to discredit Farage via his private life, accompanied with nudge-nudge wink-wink stories about his "womanising" from former colleagues.

It won't work, and will almost certainly be counterproductive. Ukip thrives as an anti-establishment party. How they have achieved it is pretty baffling: Farage's background as a public school-educated former banker hardly distinguishes him from other political leaders, and the Ukip leader has appeared on BBC's Question Time more than any other British politician. But Farage's conscious deviation from the script of how a professional politician is supposed to speak and behave endears him to voters bored of on-message Westminster clones. Voters are more likely to forgive his foibles than they are other politicians'; they can even add to his appeal. The establishment appearing to close ranks will surely help cement Ukip's insurgent image.

But whether it works or not is besides the point. It smacks of the beginning of a re-run of the sort of campaign waged against Nick Clegg in the run-up to the 2010 election. I could barely have less respect for the Liberal Democrat party, a cynical bunch of political opportunists who helped trash what little faith in politics many of the first-time young voters Clegg inspired had. But before election day, the rightwing media decided that there must be a Tory majority government, and the short-lived Cleggmania – when he enjoyed headlines suggesting he was almost as popular as Winston Churchill – was seen as a block on it. He had to be personally discredited. "Nick Clegg in Nazi slur on Britain" was one Daily Mail headline, outrageously misrepresenting a Guardian piece he had written years before. "Is there ANYTHING British about Lib Dem Nick Clegg?" screeched the Mail on Sunday because, among other things, he had a Spanish wife and Dutch mother. Donations that were already in the public domain were portrayed as somehow sinister, and so on.

Today, it is Ukip that are seen as an obstacle to Tory ambitions of a majority at the election, and that's why Get Farage is rolling. You don't have to have any sympathy with Ukip to object to this Crosbyisation of British politics, or the constant distraction from debating political issues in favour of character assassination. To only object when the left is targeted – for example, the Daily Mail's attack on Ed Miliband's father as the "man who hated Britain" – would be insincere and unprincipled. British politics has to be purged of this toxic approach.

That does not mean the personal characteristics of politicians can never be scrutinised if outright hypocrisy is involved. In the 1990s, John Major's Tories invited scrutiny of their complex private lives when they unleashed their "back to basics" family values campaign. Homophobes with a predilection for sleeping with members of the same sex are asking for it, as are politicians who bash benefit recipients while, say, using state expenses to heat their stables.

For those of us who want Ukip defeated politically, we need a different approach. Ukip is an unwieldy coalition that can be unpicked. Its leaders are rightwing libertarians who are passionate about withdrawing from the EU, but for many Ukip voters, the EU isn't even a top three concern, and on economic issues such as public ownership of rail and energy, they are firmly on the left. In our grim national so-called debate about immigrants, Farage may as well have become minister for immigration, and even he has attacked policies such as the Tories' "racist van" for being nasty. It is the insecurities driving the anti-immigration backlash that have to be addressed, such as a lack of affordable housing or secure, well-paid jobs.

But that political debate is the last thing Farage's baiters want. They promote the Ukip-isation of British politics while attempting to crush anything that gets in the way of the Conservative party's electoral plans. It may stick in the craw to defend Farage from these kind of attacks. But if we want a political debate that is honest, clean and about policies rather than personalities, the test is not defending those we agree with from personal attack, but those we bitterly oppose.