Blair, 48, is hoping he can achieve what no British Labor Party leader has done before win a second consecutive full term in office.
After the traditional visit to Queen Elizabeth at Buckingham Palace to secure her permission to dissolve parliament, Blair broke with precedent by announcing the election date at an inner-city London school instead of from his Downing Street office.
With Blair's Labor Party apparently set for election victory, Blair said voter apathy was a possible problem. "Every vote in this election is precious," he said.
The opposition Conservatives feel they can pick up votes on the back of a lack of enthusiasm for European integration, a major Labor Party goal, on the part of Britain's every day citizens. But Blair hinted he would be happy to fight on the European battleground as a proponent of closer links with the continent.
"We are not yet the leading nation in Europe that our weight, prosperity and history demand," he said. "We seek a mandate to make Britain stronger stronger because we are engaged with Europe and the wider world, showing our leadership, not in retreat."
Blair was forced to postpone the election from his preferred date of May 3 so he could turn his attention to the foot-and-mouth epidemic that has dealt a blow to Britain's farmers and the tourist trade.
Labor's poll ratings have proved immune to foot-and-mouth and other setbacks, such as protests against high fuel prices, major floods and the firing of Peter Mandelson, architect of Blair's 1997 landslide victory.
Labor is up to 20 points ahead of the Conservatives in ratings, suggesting the prime minister might even increase his 179-seat parliamentary majority, itself a 150-year high for Labor.
Blair said he had earned the trust of voters four years ago, when he scored his massive victory ending 18 years in the wilderness for Labor. "We know we still have so much to do, so many challenges to overcome," he said.
Charles Kennedy, leader of the minority Liberal Democrats, said Labor had done little to improve schools, hospitals and the transport system. He pledged to pump money into all key services even if it meant putting up taxes.
But Blair goes into the campaign boasting enviable levels of prosperity and economic stability.
The prime minister can also count among his achievements a peace accord in Northern Ireland, sealed with the help of former President Clinton.
But the peace process is in a shaky state these days, with the Protestant head of its power-sharing government, David Trimble, threatening to bolt the coalition in seven weeks unless the Irish Republican Army abides by promises to disarm.
Under Britain's parliamentary system, the prime minister does not directly campaign for election. Instead, his party must win a majority of the 659 seats in the House of Commons.
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