COLORADO SPRINGS, United States (AFP) - George W. Bush and election rival John Kerry hammered away at each other's credibility ahead of their final debate while Democrats were outraged about a new anti-Kerry documentary.
President Bush visited Colorado for his final appearances before the third debate with Kerry in the Arizona town of Tempe.
Kerry has rebounded in opinion polls for the November 2 election since the debates started two weeks ago. But the race is still too close to call with many surveys predicting a dead heat.
A CBS News poll released Tuesday gave Bush 48 percent of voter intentions and his Massachusetts senator rival 45 percent, a statistical dead heat because of the margin of error.
A host of other polls in recent days have given similarly tight results, some with Kerry just ahead.
The first two debates have been dominated by the Iraq war and security but the finale will focus on domestic issues.
Speaking in Colorado Springs, Bush said the debates had thrown the spotlight on his Democratic opponent's liberal credentials.
"These debates have highlighted the clear differences between the senator and me on issues ranging from jobs, to taxes to health care to the war on terror," Bush told a rally.
"As much as he tried to obscure it, on issue after issue, my opponent showed why he earned his ranking as most liberal member of the United States senate."
Kerry had no public appearances Tuesday but his Democratic party complained to the Federal Election Commission (FEC) about a broadcast company's plan to air a documentary critical of John Kerry so close to voting day.
Eighteen Democratic senators complained to the Federal Communications Commission (FCC), the broadcast watchdog, while the Democratic National Committee was to file a protest with the FEC.
They argued that the planned broadcast of "Stolen Honour: Wounds That Never Heal," on up to 62 stations owned by the Sinclair Broadcasting Group amounted to improper partisan political programming.
The documentary includes testimony from former Vietnam prisoners of war and their families. They argue that Kerry's 1971 testimony to Congress, criticising the war that he had just returned from, betrayed his comrades and helped prolong their captivity.
Kerry was decorated for bravery during the war but he has been sidetracked earlier in the campaign by criticism of his record.
"To allow a broadcasting company to air such a blatantly partisan attack in lieu of regular programming and to classify that attack as 'news programming' as has been suggested, would violate the spirit and, we think, the text of current law and regulation," said the Democratic senators' letter to the FCC.
The FCC said it had received the letter, but one official said it would be difficult to rule on the complaint before the 90-minute documentary is aired.
Sinclair Broadcasting owns stations reaching nearly one quarter of US television households, including markets in key battleground states.
"Characterizations regarding the content are premature and are based on ill-informed sources," it said in a statement.
In April, Sinclair refused to let its stations broadcast an edition of the ABC network's "Nightline" programme in which the names of all American soldiers killed in Iraq were read.
Campaign attacks have become increasingly personal in recent days.
On Monday, Kerry accused Bush of breaking a pledge to make OPEC hike oil production, and vowed to wean US consumers off Middle East oil, while Bush attacked Kerry on Iraq.
"I want America's energy future, I want America's security to be in the hands of Americans and in our own ingenuity, our own innovation, not the Saudi royal family or others around the world," Kerry said in New Mexico, pointing to record oil prices.
Bush continued to assail Kerry's position on Iraq as he campaigned in Hobbs, a small town on New Mexico's border with Texas, where the president has a ranch.
"With a straight face, he said he had only one position on Iraq. He must think we're on another planet," Bush said.
The conflicting opinion polls indicate however that the race is too close to call and careening to the same cliffhanger finish as four years ago when the outcome hinged on a bitter recount in the state of Florida.