With a win in tomorrow's Republican primary all but guaranteed, venture capitalist W. Mitt Romney's campaign for U.S. Senate got a boost last week when a poll showed him and Sen. Edward M. Kennedy '54-'56, the democratic incumbent, in a virtual dead heat.

The poll, taken September 8 and 9, showed that Romney has 43 percent of the vote and Kennedy has 42 percent support from the state's electorate. Opinion Dynamics, a Cambridge firm, conducted the survey.

Observers of the race said this race will be the toughest one Kennedy has ever faced.

Romney campaign officials said yesterday that the close race is due to a summer of intense campaigning by their candidate.

"Mitt has been traveling across the state getting out and meeting people and he has spent about $300,000 in an effective ad campaign," said Romney assistant press secretary Nicole St. Peter.

St. Peter said the six-term senator is running scared and is desperately trying to keep a seat he has held in the Senate for 32 years.

"They realize that this is his first real challenge," St. Peter said. "They finally realize that [Kennedy] has an opponent who is in touch with the people."

After tomorrow's primary against Republican rival John Lakian, St. Peter said the campaign will move into the general election with an energetic organization and a war chest which is increasing daily.

"We are upbeat and working hard...We are right where we want to be," St. Peter said. "We are now raising more money than Kennedy."

In fact, Romney has outpaced the Democratic icon's fundraising efforts throughout the summer.

The gap between the Republican and Kennedy is particularly large instate, St. Peter said. Much of Kennedy's fundraising money comes from outside Massachusetts, while 68 percent of contributions to the Romney campaign are from the Bay State.

Independent pollster John Gorman told The Boston Globe last week that a Kennedy advertisement emphasizing the senator's support for the crime bill had backfired.

After the Kennedy ad aired, Romney counterattacked with commercials criticizing the senator's record on crime.

"Kennedy raised an issue where he wasn't strong and said, 'Hey, look me over on this issue," and Romney counterattacked very effectively," Gorman told the Globe.

Officials in Kennedy's campaign office did not return phone calls yesterday.