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Democrat Jim Webb campaigned with presidential prospects past and future and Republican Sen. George Allen shook hands with workers at the world's largest cigarette plant Thursday as their Senate campaign neared its end.

What could be a pivotal contest in determining whether the GOP retains control of the U.S. Senate remains close, the most recent polls show. One poll showed Webb with a slight lead, and others show it within the margin of error.

In Arlington, nearly 1,000 Webb supporters packed a ballroom for a fundraiser with actor Michael J. Fox and retired Gen. Wesley Clark. More than 700 people greeted Webb, Illinois Sen. Barack Obama and former Gov. Mark R. Warner at a rally at Virginia Union University in Richmond earlier in the day.

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"Why is it the war on terrorism seems to be fought between September and November every even-numbered year?" Obama, the son of a Kenyan immigrant, said on the campus of the predominantly black private college.

Obama, a rising prospect for a possible 2008 presidential race, and Warner, who last month abandoned what had been a serious exploratory presidential campaign, lent the event the high-voltage air of a presidential campaign event.

Allen shook hands with hundreds of workers leaving from the day shift at the giant Philip Morris Co. complex in Richmond. The incumbent had also pondered presidential ambitions before what had seemed an easy re-election turned into a desperate campaign.

On Wednesday, Allen refused to denounce his supporters' manhandling of a liberal blogger and accused Webb of provoking the incident. Video of the incident was shown on cable news networks and circulated widely on the Internet, posing a late-campaign distraction for Allen.

Men wearing blue Allen lapel stickers put University of Virginia law student W. Michael Stark in a choke hold and slammed him to the floor after an Allen rally at a Charlottesville hotel Tuesday.

"It was typical of the Webb campaign, wanting to provoke an incident," Allen said Wednesday. He did not say why he believes the Webb campaign provoked the stunt.

Webb said he did not know Stark.

"I don't even know what happened yesterday. I don't even know this individual. But I certainly regret the conduct of certain people there yesterday," Webb said.

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