With a House floor debate over energy and climate change legislation only weeks away, the Obama administration must determine how much to use the president's popularity and influence to help push the bill across the finish line.

Unlike the economy, religion or the Middle East, the president so far has not given any major speeches on the often contentious environmental issue. But there is growing pressure for the White House to do more.

"For this bill to pass in either house, the president will have to reach out personally to key members, just like he did on the stimulus bill," said Manik Roy, vice president of federal outreach at the Pew Center on Global Climate Change.

Obama's efforts could help make the difference in getting to 218 votes in the House, where dozens of moderates and farm state Democrats are holding out over a plan that they do not think takes their constituents into account. And looming in the distance is the Senate, where the 60-vote hurdle will require the White House to reach out to industrial state lawmakers from both sides of the aisle.

Roy suggested Obama team up with the likes of Republican Sens. John McCain of Arizona, Lindsey Graham of South Carolina, Richard Lugar of Indiana and Lisa Murkowski of Alaska if he wants to get a climate bill through the Senate. "There's a core group of Republicans," Roy said. "Their politics are real tough, but as individuals, for different reasons, they really care about this issue. Obama needs to enter into an partnership with those people. I don't see any other way of doing this."

James Connaughton, chairman of the White House Council on Environmental Quality during the George W. Bush administration, agreed that Obama must be the one to bridge the partisan divide.

"It looks like they may be doing some shovel diplomacy among different ranks of Democrats," said Connaughton, who now manages energy and environmental issues for Baltimore-based Constellation Energy Group Inc. "Ultimately in the Senate, they've got to find some Republicans. For lasting success of the bill, they really should be trying to make it more bipartisan than what it might even be shaping up to be."

To date, the White House's biggest move in the climate debate was a subtle one when it acknowledged this spring that it was open to something less than a complete auction of the emission credits. Obama gave the signal during an April event hosted by the Business Roundtable, then elaborated as an aside during a nationally televised press conference.

Connaughton credits Obama for making the move toward compromise, though he would prefer a bit more transparency. "The fact they were so quick to abandon the 100 percent auction tells me that they're going to continue to give key signals to get a deal," he said. "It looks like they're going to parcel them out over the debate. I'd have preferred something a little bit more proactive and more public. But what they've been doing so far seems to be calibrated toward facilitating a deal."

Obama's most public move so far came as the legislation looked stuck in the Energy and Commerce Committee earlier this spring. That is when he invited all 36 of the committee's Democrats to sit down at the White House for a briefing. Several lawmakers said Obama's interest helped propel them to keep working on a compromise.

Now, with the House debate nearly ready for the floor, some say it could be useful for Obama to again step up to the plate.

House Ways and Means Chairman Charles Rangel (D-N.Y.) meets at the White House today with Obama to discuss the president's health care plans, but climate legislation also looms on Rangel's agenda after House leaders gave him a June 19 deadline to either markup the bill or cede jurisdiction.

"If the president doesn't bring it up, we will," Rangel told reporters yesterday.

Still other lawmakers would prefer for Obama to wait until the legislative debate ripens beyond the current jurisdictional turf wars.

"He'll need to speak out on climate, but I don't think he needs to do it at this point," said Rep. Rick Boucher (D-Va.). "He has a platform where his words are heard by everyone. That'll be important in order to explain the reason climate change controls are necessary. I'm not sure that while these committees are working through their processes, it's central for him to do that. But at the proper time, he will need to do that."

Senate Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) said Obama has stayed out of the climate debate on her end of Capitol Hill too. Asked when the White House should assert itself into the debate, Boxer replied, "Eventually ... I think we're doing what we need to do, which is to find out where people are. Do they want a bill? If they have a bill, what does it look like?"

Riding Air Force One

Obama this year has given lawmakers plenty of fodder as they weigh the implications of a climate bill.

Last week in Germany, for example, the president told reporters that the pace of the House debate -- with an Energy and Commerce Committee markup finished before the Memorial Day recess -- had surprised even him.

"That process is moving forward in ways that I think if you had asked political experts two or three months ago would have seemed impossible," he said. "So I'm actually more optimistic than I was about America being able to take leadership on this issue, joining Europe, which over the last several years has been ahead of us on this issue."

But Obama's Cabinet officials have also sent mixed signals. Agriculture Secretary Tom Vilsack last month broke the silence on a key detail of the House legislation, telling farmers in Kentucky that his department should have oversight of the carbon offset market rather than U.S. EPA.

And Rep. John Salazar (D-Colo.) offered a rare moment of political candor last week when he said his brother, Interior Secretary Ken Salazar, has mixed feelings about the cap-and-trade provisions of the House bill.

"Actually, I think he feels about the same way I do," Rep. Salazar said. "We want to make sure that us oil-patch Democrats are well positioned, that if we have to take a vote, that we'll take the right vote. And second of all, I'd hope we'd move the bill in the Senate before it comes to the House, because the Senate I don't think is going to pass any kind of version like the one we do."

Asked about his brother's comments, Secretary Salazar made a quick retreat.

"We are aiming in a united way from the -- from President Obama's energy team to have a good bill on cap and trade," Ken Salazar, a former Colorado Democratic senator, said. "We're committed to doing that. We know there's a process in place in the Congress, a matter of deliberation, and we hope that we get to a good cap-and-trade bill. We're all very hopeful we can get this done. It's going to be a very good bill for America."

White House officials also complained last week about a London Guardian story that said Obama would put his political chips on the line to support the global warming bill. "When the bill is further along in the legislative process there are some things where it may make a difference in expressing a strong view," White House Council on Environmental Quality Chairwoman Nancy Sutley told the newspaper. "What [Obama] has been saying consistently is that he wants a bill and that this represents a very important step forward."

Other Obama officials have been up to the Hill to talk to lawmakers. White House advisers Carol Browner and David Axelrod spoke about the national security aspects of the energy bill in late April during a briefing with senators. And U.S. EPA Administrator Lisa Jackson meets with Senate Democrats today about the legislation.

Still, it is unclear just how much Obama will need to push -- and what he stands to gain from sticking himself out too far on a bill where the public does not have a firm understanding of the details.

Obama's White House will have to make a public statement on the House bill as it comes up this summer on the floor in the form of a Statement of Administrative Policy.

Connaughton said the fact Obama has yet to step out on a limb should not be a surprise. "I see a very good and methodical organization of the use of the president's precious time," he said. "I think they've set their calendar on where they need him and when they need him in relation to the energy and climate bill pretty well."

Democrats on both ends of Capitol Hill say that Obama will eventually chime in when the votes are close.

"The president is wise in both letting people sort through this, people bring their own concepts and ideas, to flesh out where they'd like to be, to put their own imprimatur on it, to hear from various sources on it," said Rep. John Larson of Connecticut, the chairman of the House Democratic Caucus. "But at some point they need somebody to say let's come together and reason. And he's the guy."

In the House, several sources said they heard that Obama had made phone calls to wavering Democrats as the Energy and Commerce Committee debate reached its climax. But no lawmaker has yet to confirm they heard from the president personally.

Rep. Baron Hill (D-Ind.) said Obama praised his work on the legislation as the pair returned to Washington aboard Air Force One after a campaign fundraiser just days before the committee vote. "The only thing he told me was he appreciated the work I'd done on the bill," Hill said. "That's as far as it went."

Hill added, "I was on Air Force One. I guess you could count that as better than a phone call."

Reporter Noelle Straub contributed.