With her flagship project and the strength of her leadership muscle on the line, Speaker Nancy Pelosi (D-Calif.) on Wednesday launched a buzzer-beater: trying to sell skeptical members of her Caucus on sweeping climate change legislation before they break for the July Fourth recess.

The gambit appears to be working. House Democratic leaders sounded optimistic about their progress after a day of hunting intensely for new backers of the 1,200-plus-page package. The biggest bloc of holdouts has been farm-state Democrats, but Pelosi scored a critical boost Tuesday when Agriculture Chairman Collin Peterson (D-Minn.), who had led the opposition for that group, struck a deal with Energy and Commerce Chairman Henry Waxman (D-Calif.) that secured Peterson’s support.

Pelosi and her whips on Wednesday took advantage of back-to-back protest votes forced by Republicans to buttonhole wavering lawmakers. But senior Democratic aides said it was the Speaker, in particular, who was devoting her full force to the effort.

“She’s going all out,— one said.

Pelosi immediately put Peterson to work, touting the package to the Democratic Caucus in a Tuesday night meeting, to freshmen and sophomores in their respective weekly huddles on Wednesday, and in a separate sit-down with members of his Agriculture panel. “Peterson’s support has been very huge,— one senior Democratic aide said.

Pelosi also was calling in another big gun Thursday to rally support — former Vice President Al Gore, who has become the face of the effort to combat global warming. He is expected to appear on Capitol Hill today to make the case for the package.

But in a sign of the work left to be done, many moderate Democrats said they still have questions or concerns about the package and either cannot yet say whether they support it or are leaning against it.

“There’s still a lot of skepticism until we see the language,— said Rep. Stephanie Herseth Sandlin (D-S.D.), a member of the Agriculture panel and whip for the Blue Dog Coalition, a group of 52 Democrats mostly from rural areas.

Rep. Tim Holden (D-Pa.), next in line behind Peterson on the Agriculture Committee, said he is a “definite no,— and another panel member, Rep. Henry Cuellar (D-Texas), described himself as “undecided, leaning no.— Cuellar said Pelosi, in seeking his vote, advertised the changes aimed at farm-state interests, but he is still worried about the measure’s impact on consumers and said agriculture groups back home still have concerns.

Peterson told reporters Wednesday that he expects a “pretty substantial majority— of his committee to back the bill after several provisions were added to appeal to farmers and rural areas, including stripping the Environmental Protection Agency of its ability to regulate ethanol and the inclusion of lucrative agricultural carbon offsets.

“I’m not going to put a lot of pressure on people,— Peterson said of other committee Democrats. “They know their districts.—

Part of the challenge for Democratic leaders is the compressed time frame they’ve given themselves for the final sales job, especially given the complexity of the measure. At the Caucus meeting Tuesday night, Rep. Mel Watt (D-N.C.) rose to ask if anyone could explain the cap-and-trade system that is the centerpiece of the bill.

Watt, who does not serve on any of the committees that weighed in on the package, said he asked the question in jest. But it pointed to a genuine concern: “It’s a very complex piece of legislation, and I need to be able to understand it, and then I can start asking questions about it.—

Waxman and Rep. Ed Markey (D-Mass.) were still negotiating minor tweaks Wednesday in an attempt to win handfuls of additional votes, including language aiding small refineries and biomass.

“We’re into the dotting of I’s and crossing of T’s,— said Rep. Mike Doyle (D-Pa.), a key moderate who helped craft the bill and has become one of its most vocal backers. Doyle predicted that a handful of Republicans would also join them in the end.

A group of moderate Republicans also met late Wednesday with House Democratic leaders, after first being courted by Pelosi last week.

“There’s going to be some people who don’t want to be on the wrong side of history on this in the Republican Party as well,— Doyle said.

Markey, meanwhile, said the whipping efforts were aided, ironically, by numerous Republican protest votes bringing Members to the floor.

The White House was deploying its resources both on the Hill and around the country on behalf of the legislation, and that was also coming into play Wednesday.

“We are arm in arm with the White House,— Markey said.

“Everyone’s united behind this bill,— Waxman said. “We’re doing an all-out effort.—

Dozens of environmental organizations and industry groups backing the bill are making a huge push as well, both in Washington, D.C., and by generating calls into Congressional districts, organizers said.

Peterson said the Congressional Budget Office score showing the legislation would cost the average family $175 in 2020 also should help Members become more comfortable with the bill.

“The costs that are going to be generated here are going to be fairly small and considerably less than some people have been talking about,— he said, adding that some farmers will be able to make money off the carbon offsets.

Republicans and the American Petroleum Institute challenged the CBO’s numbers and charged that the bill would cost millions of jobs.

Democrats want to clear the decks for the far-reaching debate on health care reform next month.

And Peterson added that there is some urgency to pass the bill now so that Obama has something to take with him to the G-8 summit next month. “He wants something in hand to show those other people what we’re working on,— he said.

Peterson also noted that despite the tight deadline in the House, it is still early in the legislative process.

“This is not becoming law— yet, he said. “I can guarantee that this thing is going to be further refined in the Senate.—

Peterson also said that without the bill, he sees no way to prevent the EPA from moving ahead with onerous new regulations on ethanol production.

“That’s one of the reasons that I’m going along with this,— he said. “This is a huge deal to get it out of there, and I don’t think we’ll ever get it out any other way.—