One of Obama's most notable political achievements in his first year in office was persuading some key Republican-leaning business lobbies to support Democratic initiatives.Organizations like the Business Roundtable, the National Restaurant Assn., the National Federation of Independent Business and the pharmaceutical industry, for example, broke ranks with the chamber and worked with the administration on healthcare.

But in the days leading up to the Massachusetts vote, when polls showed Brown heading toward an upset, some of those groups turned back fitfully toward their Republican roots.

The National Federation of Independent Business, for example, insisted on more public criticism of the Democrats' healthcare plan.

That prompted Grover Norquist, the conservative activist who heads Americans for Tax Reform, to remark that "members are wondering why the organization was either AWOL or collaborating for months and months."

Dan Danner, president of the business group, disputed Norquist's suggestion that the organization had changed its stripes. But he acknowledged that the group's view of the Obama administration's healthcare overhaul had soured.

Danner also noted that his organization was one of the first to send personnel and money into Massachusetts to help Brown.

Conservative pressures -- and responses like the federation's -- are expected to intensify. That worries Democrats, as does the impact of the court ruling.

"The decision is a big worry for Democrats," said Michael Meehan, who has run several Senate campaigns in recent years. "It totally swings the balance.

"In a typical contested Senate race, we calculate that one-third of the spending comes from the candidate, one-third from the party and one-third from outside groups. There are still limits on the first two, but unlimited sums are allowed from corporate America," he said. "To the extent that corporations continue to favor Republicans, this is a major concern for Democrats everywhere."