News of the World backs Conservatives in election race
The News of the World and the Sun are now backing the Tories
The News of the World is backing the Conservatives in the general election, after 13 years of Labour support.
Britain's best-selling Sunday newspaper said the Tories were the best hope for a "brighter, saner, safer... future".
Its sister paper, The Sun, announced it was switching sides in September. The polls suggest the Conservatives' lead over Labour has narrowed recently.
Gordon Brown and David Cameron rallied activists at events on Saturday ahead of the election expected on 6 May.
The News of the World said the country was crying out for change and Tory leader David Cameron must by given the chance to rule, saying the modernised Tories could be a "force for good".
But it added that Mr Cameron still had much to spell out and prove. The Scottish edition of the newspaper has not endorsed any political party for the general election.
I completely accept that a lot of people still haven't made up their minds and still need to be convinced
A poll by ICM for the News of the World suggests the Conservatives had slightly extended their lead over Labour after last week's Budget - but not by enough to win an outright majority in the Commons.
The poll of 1,003 adults, taken on 24 and 25 March, puts the Conservatives on 39%, Labour on 31% and the Lib Dems on 19%.
However a YouGov survey for the Sunday Times suggested Labour had narrowed the gap - it put the Conservatives on 37%, Labour on 32% and the Lib Dems on 19%. YouGov interviewed 1,533 voters online on 25 and 26 March.
Mr Cameron told the BBC's Politics Show: "It's going to be a very exciting 40 days that we have to go between now and the election, I completely accept that a lot of people still haven't made up their minds and still need to be convinced but I think the opportunity of change is there and I hope people will grab it."
In an interview on BBC One's Andrew Marr programme, Conservative frontbencher Michael Gove acknowledged that voters wanted "more detail" of his party's plans, which he said would be set out before the election.
Gove: Winning ideas, if not polls
He said shadow chancellor George Osborne had already spelt out "the fact that there will have to be public spending restraint - in plain English, cuts" - including a rise in the state pension age and removing tax credits for some.
And he said polls suggested "there has been a bigger swing towards us in the marginals than elsewhere".
For Labour, Schools Secretary Ed Balls told the same programme there would be "tough decisions in some areas but police, NHS, schools, childcare, 16-19 [education], we're going to have protection there - rising spending from a Labour government."
He said the government would raise national insurance and the top rate of tax, which were "difficult decisions which the Conservatives want to reverse".
Asked whether he would be ready to team up with the Liberal Democrats in the event of a hung parliament, Mr Balls said: "Nobody wants to have coalitions and hung parliaments, that isn't the British way of doing things, and we don't tend to have them usually.
"And they can tend to lead to really fudged and muddled decision-making. What I want to see is a Labour majority, that's what I'm campaigning hard for.
Posters attacking Gordon Brown will go up in England and Wales from Monday
"But look, if it comes to that, what we'll need is people who are ready to go round the table and talk tough and say let's make the difficult decisions."
On Saturday, Prime Minister Gordon Brown rallied Labour activists at an event in Nottingham, where he unveiled five key election pledges and told them Labour was the "people's party".
He has not officially announced the election date but it is widely expected to be held on 6 May - and must be held by 3 June.
Lib Dem leader Nick Clegg dismissed the pledges as "vacuous" adding: "Between them Labour and the Conservatives have failed to come up with a single specific positive reason to vote for them."
Mr Cameron told his own activists on Saturday they had "40 days and 40 nights" to make the Conservatives' case to the country and said of the election: "We are ready to fight it whenever he is ready to call it."
His comments come ahead of a new Conservative advertising campaign, in which Gordon Brown comes under attack.
From Monday, posters featuring close-up images of the prime minister grinning, alongside negative claims about his record in office, will go up at 850 sites in England and Wales
Slogans will include: "I took billions from pensions - vote for me" and "I let 80,000 criminals out early - vote for me".
The campaign, created by M&C Saatchi, follows earlier posters with close-up shots of David Cameron, which led to accusations of airbrushing by Labour.
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