The latest polling has mixed results for Mr. Blair, who is trying to become the first Labor Party prime minister to win three straight elections.
The polls point to a Blair victory, with a plurality of likely voters saying they prefer Labor over the main opposition Conservative Party, and the left-of-center Liberal Democrats.
But a survey in the Financial Times newspaper also finds that more than a third of those likely to vote say they could change their minds, with only one day of campaigning left.
Labor currently holds a 161-seat majority in parliament, but some opinion polls have suggested that advantage could be cut in half by the election. Even that result would leave Mr. Blair with a comfortable margin of victory.
But the prime minister is crisscrossing the country at a frantic pace, warning Labor voters against complacency and apathy.
And Mr. Blair's most controversial decision, to go to war in Iraq, continues to command attention in the campaign.
In the latest twist, the widow of a British soldier killed in Iraq Monday has come out against Mr. Blair. In a series of interviews on British television networks, the widow, Ann Toward, has said she would like to tell Mr. Blair he was wrong to join the U.S.-led invasion.
"I would say, 'You should not have sent them troops over," Ms. Toward says. "You should never have done that. If it was not for you, today my children would still have their father.'"
Mr. Blair has expressed his deep condolences to the family, while praising the role of the British military in Iraq.
"The British soldiers have done an extraordinary job in Iraq, helping that country become a stable democracy, and I totally understand the grief and distress of people who are bereaved by soldiers that have lost their lives doing their duty for their country," Mr. Blair says.
Relatives of several soldiers killed in Iraq organized a visit to Mr. Blair's London office to present a legal claim they plan to file against him for what they call, in their words, "deception that led to war."
And in Mr. Blair's home constituency, in Sedgefield in northeastern England, the father of a soldier killed in the war is running as an independent candidate against the prime minister.
Despite much media focus on Iraq during the campaign, pollsters say the war is not a major concern of most voters. It ranks it near the bottom of their electoral priorities, well behind issues such as health care and education.