Election 2015: I will put country first - David Cameron
David Cameron has insisted he will "put the country first" if he fails to win an outright majority on Thursday.
But Mr Cameron said he would not dwell on "predictions" about what would happen if there were a hung parliament, as he urged voters to "shape the future with your vote".
In a last push ahead of polling day, he said only a Conservative government could keep the country moving forward.
And he again warned of the "chaos" of a Labour government supported by the SNP.
The prime minister has embarked on a 36-hour trip before voters head to the polls on 7 May.
He addressed crowds of supporters and the public at rallies in Twickenham, south-west London and Hendon in the north of the capital.
At one point he was heckled by an SNP supporter who accused the Conservatives of stoking up racism over its Labour/SNP deal claims.
Meanwhile, Lib Dem leader Nick Clegg has started a "two-day dash" from Land's End to John O'Groats and Labour leader Ed Miliband has targeted key seats in the south of England.
On the campaign trail in London, Mr Cameron urged voters to "judge us on our record, have a look at our plans and think about the choice".
He said he was not claiming the government had "solved every problem" in the country, as there was still "huge amounts" to do.
Travelling with the Conservative leader: Carole Walker, BBC political correspondent
David Cameron's final non-stop 36-hour drive for votes began at a garden centre in Twickenham, south-west London, in the constituency of Vince Cable - one of the Liberal Democrat ministers he is hoping to oust from power.
It was a lively start with a Scottish heckler objecting to the tone of Mr Cameron's warnings of the dangers posed by the SNP, accusing him of racism. Security staff escorted the man away and the prime minister moved on to north London where he stuck to that core message of his campaign.
At a high-tech office in Hendon he repeated those warnings about the dangers of a Labour government propped up by the SNP. No matter that Ed Miliband has ruled out a deal with the Scottish Nationalists, Mr Cameron said Labour would be dependent on its votes. He warned north London voters that their local rail and tube improvements would be in jeopardy with the SNP interested only in funding projects north of the border.
London Mayor Boris Johnson came along to rally support, weighing in with a vivid evocation of Alex Salmond with his feet up in Downing Street and a glass of pink champagne in hand, calling the shots for Ed Miliband.
There were tough questions too about why voters should put their trust in a bunch of people who all went to the same school and look after their friends in the City. But most of the questions were about what Mr Cameron would do if he fails to win an outright majority, as the polls suggest.
He refused to be drawn, insisting the real choice was between him or Ed Miliband as prime minister - a choice he said was between stability under his leadership or chaos under any of his rivals.
It is a message he will be repeating today, tonight and tomorrow as he campaigns in many of the key marginal seats he needs to win if he is to win a second term in power.
But he said 1,000 jobs a day had been created under his watch, and the UK economy had grown faster than any other major Western economy.
"Let's take that track record and turn it into something really exciting for families up and down our country," he urged, warning that a Labour government would put it all "at risk".
Asked to give a view on the constitutional position if no one party won a majority on Friday, Mr Cameron replied: "You are in the prediction business and you can make lots of predictions in the next 36 hours.
"I am in the business of saying to people... don't talk about predicting the future - shape the future with your vote. There is still time to determine the outcome of this election."
But after a member of the audience complained that politicians never gave straight answers, Mr Cameron said: "I put the country first, I formed a coalition [in 2010].
"I did what was right to give strong government for Britain. So I will always put the country first."
With the polls pointing to the likelihood of there being no outright winner on Thursday there has been much discussion about what deals the parties may do with each other to form a government.
Mr Cameron reiterated his warning about the prospect of a minority Labour government propped up by the SNP, predicting that it would lead to "chaos".
He said the SNP would hold Labour and country "to ransom", with higher borrowing, more taxes and weakened defences.
And he sounded a note of caution about the Liberal Democrats too, saying Nick Clegg's party was just as likely to support Ed Miliband and the SNP as they would the Conservatives.
"Thursday is decision day. You can have the strong, competent capable government with the Conservatives that keeps our economy moving forward, or you can put it at risk with Labour and the SNP," he said.
Meanwhile, SNP leader Nicola Sturgeon said Mr Cameron's election campaign had "descended into desperation".
She told voters they had "48 hours to get the Tories out", and questioned the legitimacy of a UK government which did not include Scottish MPs.