As a five-term Senator and chairman of the Senate Finance Committee, Montana Sen. Max Baucus wields plenty of clout in Washington, D.C.

But last week it was his position as a swing vote on the Senate Environment and Public Works Committee that may have meant life or death for a mandatory cap and a credit trading system for greenhouse gases.

He announced Wednesday that he would support the measure -- "America's Climate Security Act -- sponsored by Sens. Joe Lieberman, I-Conn., and John Warner, R-Va.

Until recently, backers of a cap to reduce the impact on carbon emissions on global warming had counted Baucus as a probable "no" vote. As a senator up for re-election in a coal-rich state, it was largely expected that the moderate Democrat would be leery of potentially costly caps.

Just the week before Wednesday's hearing, Baucus was noncommittal, telling a reporter that while the Lieberman-Warner effort was "interesting," he didn't yet know if he would vote for it.

What made up his mind, he said Wednesday, was his work with the sponsors to ensure sufficient incentives for the development of carbon capture and sequestration and opportunities for Montana farmers and foresters to create carbon offsets such as no-till farming. He said he's still concerned about providing protection for Montana's rural electric cooperatives from rising energy prices.

Lieberman and Warner were delighted with Baucus' decision. "It is a tremendous boost to our efforts to get a real solution passing in this Congress," Lieberman said.

We, too, are glad to see progress made on a substantial response to global warming, although many potential political roadblocks remain. And we agree with Baucus that "Even if another coal-fired power plant was never built in the U.S., China would continue to develop their coal resources. We must develop carbon capture and sequestration technology here so that we can use it domestically, as well as export it abroad."

Plenty of details remain to fight about, but the legislation's general outlines have significant support from many environmental and industry groups. It looks as though the Climate Security Act has a much better chance to prevail than other efforts in recent years.

We hope it does. As Baucus said last week, addressing climate change is nothing less than a "moral imperative."