WASHINGTON — The already long odds that U.S. President Barack Obama would win passage of significant climate change legislation soon are getting longer.

Obama has been weakened by the loss Tuesday of a Senate seat held by Democrats for more than a half-century. Even before the vote, he was struggling to persuade some fellow Democrats to make climate change legislation a priority. That will be even harder after Tuesday's vote, which has made Democratic lawmakers more hesitant to follow the president's lead.

The loss in Massachusetts has been widely interpreted as a rejection by voters of Obama's sweeping ambitions, particularly of the massive health care bill that has dominated the first year of his presidency. That legislation is now in doubt. Its possible collapse has made Democratic lawmakers reluctant to take on contentious issues ahead of congressional elections in November.

"It's hard to see now how climate change gets on the agenda," said Adele Morris, policy director for climate and energy economics at the Brookings Institution. "Unless something changes, nobody is going to want to take this up ahead of the elections."

Senior democratic lawmakers already are openly discounting the chances for a bill that would cap emissions. Many are recommending less controversial legislative goals to build momentum and win victories before congressional elections in November. They want to see bills to deal with the ailing economy and high unemployment, both of which are angering voters, and they worry that Republicans will paint efforts to cap carbon emissions as job destroyers.

Still one analyst thinks that some lawmakers will be pushing for a bill despite the challenges, because chances of passage are not likely to improve later in Obama's presidency.

"Time is running out for the Democrats to pass something," said Kevin Book, managing director of research at ClearView Energy Partners LLC. "The setback has made it less likely they will succeed, but not less likely that they will try."

The dimming prospects of U.S. legislation will complicate international efforts to negotiate a global climate treaty to limit emissions. A December climate conference in Copenhagen, Denmark, ended without a deal on mandatory cuts. Disputes between rich and poor countries and between the world's biggest carbon polluters — China and the United States — dominated the two-week conference. Without signs that the United States is moving toward mandatory carbon caps, the rest of the world is less likely to follow. (AP)