LONDON – Prime Minister Blair asked for a third term yesterday, calling a national election for May 5 that he is expected to win despite the unpopular Iraq war, continued public grumbling about public services, and an apparent drop in his opinion poll lead.

“It’s a big choice and there’s a lot at stake,” Mr. Blair said after Queen Elizabeth II granted his request to dissolve Parliament. “The British people are the boss and they are the ones who will make it.”

Mr. Blair is seeking a third term in office – his last, he has said – after eight years in power, commanding a huge majority in the House of Commons.

Opinion polls published yesterday showed Mr. Blair’s Labour Party running anywhere from two points to five points ahead of the opposition Conservatives – more or less a statistical dead heat.

But Britain’s electoral system favors Labour, whose share of the vote is spread more efficiently across the country, and analysts say Conservative leader Michael Howard needs to grab a lead of around eight points to have a shot at winning. It is more likely, analysts say, that Mr. Blair will win with a reduced majority in the Commons.

Still, Mr. Blair’s position is nothing like the double-digit poll leads Labour racked up before the 2001 election. And he may be vulnerable to apathy among his supporters – a MORI poll showed Conservatives more likely to vote than Labour supporters.

“Hardworking families – honest people who do the right thing, who respect others, who provide for their children, who look after their homes, and contribute to their communities – are being taken for granted by Mr. Blair,” Mr. Howard said.

Mr. Howard has highlighted issues including immigration, education, and health care. But he has been unable to capitalize on discontent about the Iraq war, because he and his party supported it.

Britain’s participation in invading in Iraq, based on what proved to be false claims that Saddam Hussein threatened the region with weapons of mass destruction, overshadowed Mr. Blair’s second term.

Critics accuse Mr. Blair of strong-arming his attorney general to declare that the war was legal. The prime minister denies any such pressure.

The government has also faced accusations, ruled unfounded by several official inquiries, that it manipulated shaky intelligence on WMD to bolster the case for military action.

Mr. Blair changed Britain’s political landscape early in his first term, winning referendums to give a degree of self-government to Wales and Scotland, and then coaxing Northern Ireland’s parties into a peace agreement which still holds despite the collapse of local government there.