WASHINGTON - Minutes after the Senate rejected a huge, controversial Republican budget-cutting plan last week, Democrats pounced hard, blasting moderate GOP senators who supported the package.

"It is now official -- Dick Lugar supports the extremists in his party over the people of Indiana," said a statement from Democratic Senatorial Campaign Committee spokesman Eric Schultz about the veteran Indiana Republican. "He will be explaining today's vote for the next 19 months."

Democrats aimed similar artillery at Republican Sens. Olympia Snowe of Maine and Scott Brown of Massachusetts. All three are up for reelection next year, and they're running scared. Because Democrats aren't the only ones firing away at moderate Republicans these days; the pressure is on from both sides.

The Tea Party Express, part of the grass-roots conservative movement that helped topple several prominent GOP candidates last year, already is opposing Snowe and Lugar. In response, they appear to be building voting records that are more doctrinaire conservative than their pasts.

But if senators such as Snowe, Brown and Lugar lean too far to the right to appease the pressure from the Tea Party movement, they risk losing moderate voters, who are crucial to general election victories in their diverse states.

The Senate took two major budget votes Wednesday. All three senators joined most of their GOP colleagues in backing the Republican plan to ax more than $60 billion from current-year spending. All three opposed a Democratic alternative to cut only $6.5 billion instead.

After the vote, the Democratic Senatorial Campaign Committee sent out detailed statements listing potential trouble for Indiana, Massachusetts and Maine if the GOP plan is enacted: thousands of lost jobs, and less funding for early childhood programs, job training and so on.

Republicans countered that their approach was a small first step toward fiscal discipline, a strategy that they said would boost the economy eventually.

"Our senators can make the case they're voting on principle," said Brian Walsh, a spokesman for the National Republican Senatorial Committee.

But last week's vote didn't erase what Tea Party backers see as these moderates' troubling pasts. The Tea Party Express, based in Sacramento, Calif., contends that Snowe and Lugar simply aren't conservative enough.

Levi Russell, Tea Party Express spokesman, said the group would devote "significant resources" to defeating Lugar and Snowe, including volunteers, phone banks and ads. Challengers to Lugar and Snowe for their party's nomination to run again are emerging in both states, but it's unclear at this early stage whom Tea Party backers would support.

Tea Party challenges remain stark in the minds of GOP moderates because they saw two of their colleagues -- Utah's Robert Bennett and Alaska's Lisa Murkowski -- defeated for re-nomination last year by little-known candidates with Tea Party support. Murkowski then mounted a write-in campaign and won the general election.

"Bennett was the wake-up call for Senator Snowe," said Mark Brewer, an associate professor of political science at the University of Maine.

Brown, 51, was a Tea Party favorite when he ran last year to complete the late Sen. Edward Kennedy's term through 2012, and he isn't a Tea Party Express target at this point.

Snowe, 64, a three-term veteran, and Lugar, 78, a six-term senator, said that the political heat didn't bother them.

They're used to it. Snowe voted against GOP-majority positions on key votes 27.2 percent of the time last year, according to Congressional Quarterly, the independent news-research service. That was the third-highest Republican Senate opposition score. Brown was fourth, at 22 percent, and Lugar sixth, at 15.9 percent.

Asked whether he felt political pressure because of his budget votes, Lugar said, "None particularly." He said voters would understand: "People in Indiana have assumed I would vote for the Republican position."

"I don't feel any pressure," Snowe said. "Every vote I make is subject to all kinds of speculation. If I worried about that all the time, I may as well give up."