WASHINGTON — With the help of five Republican senators, two of them from Maine, the Democrat-controlled Senate defeated a bid Wednesday to block the Environmental Protection Agency from setting the first federal standards to reduce toxic air pollution from power plants.

Republicans were behind the effort, but they didn’t get enough votes to move ahead. It was the second time in this Congress that Senate Republicans failed to muster a majority to scrap an Obama administration rule aimed at curbing air pollution from primarily coal-fired power plants.

Joining the Democrats to defeat the bill were Sens. Susan Collins and Olympia Snowe of Maine. Republicans Kelly Ayotte of New Hampshire, Scott Brown of Massachusetts and Lamar Alexander of Tennessee also voted against the bill.

The White House, in a statement released Wednesday, said that the outcome shows “a bipartisan group of senators stood with President Obama supporting sensible steps to reduce dangerous pollution” and “against misleading attacks.”

The measure would have overturned a long-overdue regulation to slash mercury and other toxic emissions from the oldest and most polluting oil- and coal-fired power plants. Since 1990, the EPA has had that power, and in 2000 concluded that such action was necessary.

But it wasn’t until late last year that the Obama administration approved new regulations, after a court threw out an attempt by the Bush administration to exempt power plants from such controls. Obama, in a video released at the time, said his administration had enough of the decades of delays caused by special interests.

In a veto threat this week, the White House said the GOP attempt, if successful, could have prevented the government from ever controlling toxic power plant pollution.

Power plants are the largest remaining source of man-made mercury in the environment. Mercury is a toxic metal that’s known to impair brain development in children, including those exposed in the womb.

Snowe issued a statement Wednesday saying that the EPA rule helps protect the people of Maine, which is downwind of many of the power plants that release the harmful emissions.

“While many parts of the country rely on coal power, the health effects from this relatively inexpensive resource are borne by the people of Maine and I have led the effort in the Senate to reduce this pollution,” Snowe said in the statement. “It is unacceptable that these costs are simply transferred from one region to another and that is why I have long supported reducing mercury pollution with cost-effective technologies.”

Collins said Wednesday voting in support of the EPA mercury standards was important for Mainers back home, who she said live “at the end of our nation’s ‘air pollution tailpipe,’” downwind from coal-fired power plants in the South and Midwest. She noted that the Clean Air Act was authored more than 40 years ago by former Maine Sen. Ed Muskie.

“Half of U.S. man-made mercury, one of the most persistent and dangerous pollutants threatening our health and environment today, comes from coal-fired power plants, and the standards will remove over 90 percent of this mercury,” Collins said in a prepared statement.

Collins said she supports “sensible regulatory reforms” that analyze the cost and benefits of proposed regulations, including the impact on job creation and consumer prices.

“When it comes to the air we breathe, however, I reject the false choice of pitting the environment against the economy because we understand that for much of the state of Maine, the environment is the economy,” she said.

Environment Maine issued a statement Wednesday afternoon praising Collins and Snowe for voting against the bill. Pollution generated by power plants in the Midwest drifts east over Maine, the group said, which is why mercury levels in Maine fish and birds, including loons and eagles, are among the highest in North America

“This is a big victory for Maine’s health and environment,” Ben Seel, clean energy organizer for the group, said Wednesday. “[The bill] would have been pretty devastating to the Clean Air Act. We’re very happy to see Sens. Snowe and Collins vote against this.”

ConservAmerica, a national organization of Republicans that support conservation efforts, also applauded the outcome of Wednesday’s vote.

“Cleaning up pollution that blows across state lines protects the health of American families in downwind states, reduces health care costs, supports jobs, and encourages a diverse mix of energy resources,” David Jenkins, ConservAmerica vice president for government affairs, said in a prepared statement. “The five senators are thoughtful conservatives who recognize the value of stewardship and who will not be bullied by out-of-state special interests. We need more like them.”

The American Lung Association of the Northeast and Waterkeeper Alliance also issued statements Wednesday in support of the measure’s defeat.

Republicans argued unsuccessfully that the benefits of the regulation did not outweigh rising electricity bills, the lost jobs from power plants shutting down and its nearly $10-billion-per-year cost. They portrayed the regulation as an effort by the EPA to kill coal, which is responsible for nearly half of U.S. electricity production. But changing economics, such as low natural gas prices and reduced electricity demand, are big factors in older coal-fired power plants shutting down.

“If you vote against this … you are effectively killing coal in America,” said Sen. James Inhofe, R-Okla., the sponsor of the bid.

The 46-53 vote was four short of the 50 needed to proceed to a vote on the resolution. Five Republicans voted against moving ahead, but five Democrats sided with Republicans in support of it.

Bangor Daily News writers Bill Trotter and Seth Koenig contributed to this report.