Election 2010: David Cameron 'giving it everything'
Conservative leader David Cameron: "Energy, energy, energy"
Tory leader David Cameron says his party now have "momentum" and he is "giving it everything" in the final week of the election campaign.
Nick Clegg told supporters in Somerset "the sky's the limit" for the number of seats the Lib Dems might get.
Labour's Gordon Brown, in the north-east of England, said he is determined to fight every minute of every day.
During one event in Sunderland, a heckler was thrown out after he tried to interrupt Mr Brown during a speech.
Entreating the audience at the National Glass Centre to vote Labour, Mr Brown said: "We must maintain the economic recovery and never put it at risk."
He carried on talking as Julian Borthwick from London tried to shout him down before being man-handled out of the room.
Mr Brown was out campaigning as two broadsheet newspapers ditched their support for Labour with The Guardian backing the Liberal Democrats, saying it supported their stance on electoral reform.
And The Times has thrown its weight behind the Conservatives, saying leader David Cameron was ready to govern.
Mr Brown told the BBC he was not worried by the newspapers' failure to endorse him. He said his concerns were to talk to electors who cast their vote next Thursday.
Scuffle at Clegg campaign event
Nick Clegg hailed the Guardian's decision to back the Lib Dems as a "significant" moment for the party.
"That is a sign of what's going on in many homes and families up and down the country," he said.
In an interview with the paper, Mr Clegg said he was "going for broke" to get the most votes, claiming the election was now a two-horse race between the Conservatives and the Lib Dems.
In an accompanying editorial, the Guardian "enthusiastically" backed the Liberal Democrats on the basis of the party's push for electoral reform.
On the campaign trail, Mr Clegg told voters in Newport not to vote tactically.
"This time we have a once in a generation opportunity to change things for good, and so this time vote with your heart."
But visiting Worcestershire later, Mr Clegg was briefly heckled and later involved in heated exchanges with a man who criticised his party's policy on immigration and prison sentences.
A heckler was thrown out of Gordon Brown's event in Sunderland
Meanwhile, the Times came out in support of the Conservatives for the first time since 1992.
Mr Cameron toured a farmers' market in Woodstock, in his Witney constituency, on Saturday, saying his party now had "momentum" behind it and he was approaching the final days of the campaign with "energy, energy, energy".
Asked about making deals with the Liberal Democrats in the event of a hung parliament, he said he was not thinking about it because he was focused on securing victory for his party.
"That is good for the country, it needs strong leadership in uncertain times."
During a later visit to a medical practice in east London, Mr Cameron pledged to protect spending on the NHS, describing it as the "most important area of our national and public life".
"It [the NHS] is the thing I care about most, that my family values most," he said.
With the final televised debate complete, and three days after Mr Brown's "bigot" comment threatened to derail Labour's campaign, the latest opinion polls suggest the Conservatives remain some way ahead but that the election could still produce a hung Parliament.
An ICM poll for the Sunday Telegraph puts the Conservatives on 36%, up one point on last week, Labour on 29%, up three points and the Lib Dems on 27%, down four points.
A Comres poll for the Independent on Sunday and Sunday Mirror suggests the Conservatives are on 38%, up two points, Labour on 28%, down one and the Lib Dems on 25%, down one.
Prime minister Gordon Brown: "I've had a wonderful reception in the North East"
A YouGov poll, meanwhile, for the Sunday Times suggested the party ratings are unchanged from a week ago with the Conservatives on 35%, Labour on 28% and the Liberal Democrats on 27%.
The BBC's polling expert David Cowling said the polls suggested two trends - that Conservative support may be hardening while backing for the Lib Dems may be slipping.
Visiting the north east of England, Mr Brown said people in the region were focused on "jobs, jobs and jobs".
Stressing the government's "rescue" of Newcastle-based Northern Rock, he said the Conservatives would abolish the regional development agency and had singled out the region for cuts.
He told workers at Tesco that he believed people were "taking time" to make up their minds on who to vote for because of the economic situation.
"My message to you is we're on the road to recovery," he said.
Accompanying him, Business Secretary Lord Mandelson denied Labour was "losing" the election and branded Lib Dem policies a "joke".
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