US President George W Bush and his challenger John Kerry are kicking off multi-state tours, as the race for the White House moves into a new phase.
President Bush will visit four states in two days
Mr Kerry embarked on a two-week tour the day after officially accepting the Democratic Party nomination.
Mr Bush rallied supporters in Missouri, resuming his campaign after spending the week at his Texas ranch.
A poll suggests Mr Kerry and running mate John Edwards have widened a small lead over Mr Bush and Dick Cheney.
"I will begin by telling the truth all across America," Mr Kerry told a launch rally in Boston on Friday, before he and Mr Edwards left for Pennsylvania.
Over the next two weeks the pair will cover 3,500 miles (5,600km) and 21 states between them.
Mr Bush began his two-day tour rallying supporters in Missouri.
"I am asking for your vote because so much is still to do - peace, prosperity - we have so much to do to take this country forward," he said.
He was due in Michigan later on Friday - another key battleground state.
On Saturday, he will visit Ohio - his second bus tour of the state in three months - before wrapping up two days of campaigning with a rally in Pennsylvania.
Kerry in the spotlight
In a major speech ending the Democrats' convention in Boston, Mr Kerry promised to fight for a stronger America, criticising the president's handling of the Iraq war and the war on terror.
Mr Kerry hopes the publicity of the last few days will provide a surge in public approval, known as a "bounce".
On Friday morning, a Zogby America survey, which canvassed opinion before Mr Kerry's speech, gave the Democratic ticket a 48%-43% lead over Mr Bush and Vice-President Cheney.
That is a three percentage point drop for Mr Bush compared with a similar poll in early July that gave Mr Kerry a 48%-46% lead.
In his speech on Thursday, Mr Kerry drew on his experiences as a soldier in the Vietnam War.
"I defended this country as a young man and I will defend it as president," Mr Kerry said.
He sought to contrast himself with Mr Bush by highlighting the faulty intelligence used by the administration ahead of the Iraq conflict.
"I will immediately reform the intelligence system so policy is guided by facts and facts are never distorted by politics," he said.
The BBC's Rob Watson says Mr Kerry's speech went down extremely well with delegates, but the question now is how will it have played in the wider country.
WEEKEND CAMPAIGN STOPS