US Republican vice-presidential nominee Sarah Palin has accused the Democratic presidential candidate, Barack Obama, of associating with terrorists.
She said he had been "palling around" with an ex-member of US-based militant group Weather Underground, which opposed the Vietnam War in the 1960s.
Mr Obama once served on a charity board with a member of the group, but he has denounced its activities.
A Democratic spokesman accused the Republicans of gutter politics.
"What's clear is that John McCain and Sarah Palin would rather spend their time tearing down Barack Obama than laying out a plan to build up our economy," Hari Sevugan said.
Commentators say Mrs Palin's attack forms part of a broader Republican strategy to attack Mr Obama's character.
Denunciation
Speaking to supporters in Colorado and later in a Los Angeles suburb, Alaska Governor Palin said the time had come to take the gloves off.
She attacked Senator Obama over his link to Bill Ayers, a founder of the Weather Underground, which waged a violent campaign against the Vietnam War.
The group was blamed for a number of bombings in the US in the 1960s.
Mrs Palin described Mr Obama as someone who saw the US "as being so imperfect... he is palling around with terrorists who would target their own country".
Mr Obama served on a charity board several years ago with Mr Ayers, who is now a professor at the University of Illinois.
The White House hopeful, who was a child when Weather Underground was active, has denounced Mr Ayers' radical past.
Focus on healthcare
The Alaska governor also said she wished the McCain campaign had not this week pulled out of the battleground state of Michigan, effectively conceding it to the Democrats.
Mr Obama meanwhile attacked the healthcare plans of Republican presidential nominee John McCain.
Speaking to some 18,000 people at a rally in Virginia, Senator Obama described the Arizona senator's policy as "radical" and claimed 20 million people would be left out by it.
A spokesman for Mr McCain, who is in his home state preparing for Tuesday's second presidential debate, said that was "a bald-faced lie".
Healthcare is important to voters and the Obama campaign has unveiled new adverts attacking Mr McCain on the issue in every battleground state.
Mr Obama's Virginia rally came ahead of a Monday deadline for voters to register there and in more than a dozen other states, including Pennsylvania, Michigan, Ohio, Indiana and Florida.
Voter turnout could be vital in deciding the outcome of the 4 November presidential election.
Meanwhile, viewing figures show a record 69.9 million people tuned in to watch Mrs Palin take part in Thursday's televised vice-presidential debate with Democratic nominee Joe Biden.
-BBC
She said he had been "palling around" with an ex-member of US-based militant group Weather Underground, which opposed the Vietnam War in the 1960s.
Mr Obama once served on a charity board with a member of the group, but he has denounced its activities.
A Democratic spokesman accused the Republicans of gutter politics.
"What's clear is that John McCain and Sarah Palin would rather spend their time tearing down Barack Obama than laying out a plan to build up our economy," Hari Sevugan said.
Commentators say Mrs Palin's attack forms part of a broader Republican strategy to attack Mr Obama's character.
Denunciation
Speaking to supporters in Colorado and later in a Los Angeles suburb, Alaska Governor Palin said the time had come to take the gloves off.
She attacked Senator Obama over his link to Bill Ayers, a founder of the Weather Underground, which waged a violent campaign against the Vietnam War.
The group was blamed for a number of bombings in the US in the 1960s.
Mrs Palin described Mr Obama as someone who saw the US "as being so imperfect... he is palling around with terrorists who would target their own country".
Mr Obama served on a charity board several years ago with Mr Ayers, who is now a professor at the University of Illinois.
The White House hopeful, who was a child when Weather Underground was active, has denounced Mr Ayers' radical past.
Focus on healthcare
The Alaska governor also said she wished the McCain campaign had not this week pulled out of the battleground state of Michigan, effectively conceding it to the Democrats.
Mr Obama meanwhile attacked the healthcare plans of Republican presidential nominee John McCain.
Speaking to some 18,000 people at a rally in Virginia, Senator Obama described the Arizona senator's policy as "radical" and claimed 20 million people would be left out by it.
A spokesman for Mr McCain, who is in his home state preparing for Tuesday's second presidential debate, said that was "a bald-faced lie".
Healthcare is important to voters and the Obama campaign has unveiled new adverts attacking Mr McCain on the issue in every battleground state.
Mr Obama's Virginia rally came ahead of a Monday deadline for voters to register there and in more than a dozen other states, including Pennsylvania, Michigan, Ohio, Indiana and Florida.
Voter turnout could be vital in deciding the outcome of the 4 November presidential election.
Meanwhile, viewing figures show a record 69.9 million people tuned in to watch Mrs Palin take part in Thursday's televised vice-presidential debate with Democratic nominee Joe Biden.
-BBC
) on live tv few times during the debate 
