Nigel Farage's Ukip is on the march, says The Observer. Last week, the Tory defector Douglas Carswell convincingly won the Clacton by-election, becoming the country's first Ukip MP.
Meanwhile, in Heywood and Middleton, a 36% swing to Ukip "slashed" the Labour majority in one of its safe seats to 617. Since then the party has "surged" in the polls, says Alberto Nardelli in The Guardian, and it is now "consistently in the mid-teens". Research firm Survation even had it on 25%.
However, due to Britain's first-past-the-post voting system, whereby a party must come first in a constituency in order to win that location's seat, Ukip's parliamentary presence, proportionally speaking, will be "nowhere near 15%, let alone 25%".
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So, who should be most worried? Nigel Farage claims that he poses an equal threat to Labour and the Tories, but David Cameron has far greater cause for concern, since Ukip's strongest support is in Conservative areas, says Peter Kellner in The Times.
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Still, there is as much point arguing about this as there is to "two men quarrelling about whether it is better to be hit over the head with a hammer or clobbered with a cudgel", says Andrew Rawnsley in The Observer.
Both parties are "nursing sore heads and neither evinces much sign of having a coherent strategy for arresting the onward march of the Faragistes". It may be an exaggeration to say that the mould of British politics has been broken, but it certainly has a "dirty big crack in it".
The main Westminster parties have much to answer for in explaining the rise of this anti-immigration, anti-European party, says The Observer. The common theme uniting the Tories and Labour is their "negativity".
The Tory strategy has been to focus relentlessly on Labour's economic incompetence; Labour's strategy has been to depict the Tories as defenders of the rich. The failure of either party to come up with a "convincing, positive vision for Britain" has left the door wide open for challengers championing a "populist, anti-politics-as-usual narrative".
Ukip's central premise that immigrants and European bureaucrats are responsible for our woes seems to have the potential to "resonate strongly with the core vote of both main parties".
Instead of taking on Ukip head-on, Miliband and Cameron appear to be allowing the party to set the agenda for the general election. This is a depressing development.
It is, agrees Yasmin Alibhai-Brown inThe Independent on Sunday. "Blaming the outsider when times are hard is a common human response. But good leaders step in to temper those resentments."
It's time for the leading parties to fight back and "expose the real messages and prejudices behind the veil of respectability worn by Farage". Most Britons have not fallen for him. "They matter too."
