By James Chapman and Daniel Martin and Jack Doyle Time to get tough: Prime Minister David Cameron and his wife Samantha Cameron Senior Tories say David Cameron should commit to backing an exit from the EU if he fails to negotiate a looser, more trade-based relationship with Brussels. Voters may not be convinced by his pledge of an in/out referendum by 2017 unless he toughens his stance, they say. After Nigel Farage's advances in local and European elections, MPs also say victory in next week's by-election in Newark is vital to burst the Ukip bubble. Mr Cameron said the message from voters had been 'absolutely received and understood'. He said: 'People are deeply  disillusioned with the European Union, they don't feel that the current arrangements are working well enough for Britain.
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Voters may not be swayed by in/out referendum promise, say senior Tories
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Conservatives need a victory in Newark by-election to halt Ukip advance
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The party is facing another coalition even if it triumphs in general election
There will be other seats where @placeholder might choose not to field a candidate and where Ukip is strong.