WASHINGTON - The Bay State's two senators are expected to emerge among the biggest winners on Capitol Hill if, as expected, Democrats regain control of the Senate.

Democratic Sens. Edward M. Kennedy and John F. Kerry would each assume the chairmanship of key Senate committees in the anticipated takeover - vastly increasing their political clout and visibility.

But yesterday, as the news of Sen. James Jeffords (R-Vt.) and his expected defection from the GOP swirled across Capitol Hill, political veterans Kerry and Kennedy were taking a cautious approach.

"Things are looking better," said Kennedy. "But let's let things clarify. I think we should let Senator Jeffords speak - then things will become exceedingly clear."

Kerry said he didn't want to say anything that might jeopardize the Jeffords move.

"Until Jeffords makes his announcement, I have nothing really to say," said Kerry. "It's all speculative. I'm superstitious and I don't want to go there."

Despite such careful words, Democrats seemed delighted at the prospect of their party taking control of the Senate as a counterbalance to Republican control of the House and the White House.

"I hope this forces President Bush to the middle," said U.S. Rep. Michael Capuano (D-Somerville). "I hope it emboldens those other Republican moderates who have all but disappeared. We need them now."

The all-Democratic Massachusetts House delegation hopes the Senate trend of GOP slippage spreads to the lower chamber.

"These things can take on momentum," said Capuano. "We will be looking to build on it. There will be some more shoes to drop. This won't be the last one."

Kennedy would be propelled back into the chairmanship of the Health, Education, Labor and Pensions committee.

Kennedy's post would put him at the center of landmark battles over prescription drugs, health care coverage and education reform that are dominating President Bush's first year in office.

"It puts Kennedy in the driver's seat on a pretty large chunk of President Bush's agenda, not to mention Kennedy's own agenda," said one Kennedy adviser. "It's like an early Christmas present."

Kerry would take over as chairman of the Small Business Committee. While the panel gleans few headlines, it generates programs that provide seed money and other help for the nation's burgeoning business community. Such business ties could also provide a boost to Kerry's fund raising, which is growing as he eyes a potential White House race.

The chairmanship clearly should be a boon to Kerry's presidential prospects, giving him a Senate platform for important policy views.

The junior senator would also pick up two subcommittee chairmanships that would enhance his national profile and help him steer federal resources back to Massachusetts.

Kerry, third-ranking Democrat on the Commerce Committee, is poised to become head of the Oceans and Fisheries Subcommittee. The post is a key one for the Bay State, which is reliant on federal policy for its fishing and other maritime interests.

In the international relations sphere, Kerry would assume the chairmanship of the East Asian Affairs subcommittee, giving him a voice on a corner of the world that is viewed by American business as a vast untapped market.