With the turning leaves and the increasingly crisp fall air, nearly every day on Capitol Hill seems to bring new predictions of when Congress will leave for the year.

Nov. 7? Thanksgiving? Christmas?

The answer to those questions depends heavily on the ability of Senate Finance Chairman Chuck Grassley (R-Iowa) and House Ways and Means Chairman Bill Thomas (R-Calif.) to resolve the differences between House- and Senate-passed versions of a Medicare prescription drug bill and a crucial tax package to be attached to the energy policy measure.

“That’s good news and bad news,” noted Sen. Trent Lott (R-Miss.), a Finance member. “It’s good news because it’s down to those two guys on these two critical issues, but the bad news is they seem to have a hard time agreeing.”

Indeed, their penchant for high-profile spats has only added to the uncertainty about when Congress will adjourn for the year. And the longer Grassley and Thomas spend on Medicare and energy means next year will only be equally cluttered with their panels’ other crucial priorities, such as a corporate tax bill needed to avoid international trade sanctions and a reauthorization of the 1996 “Welfare to Work” law.

“Quite frankly, in my mind, energy and Medicare are much more important than [the corporate tax bill] and welfare,” said Grassley. “So I accept what [GOP leaders] want me to do, but you can only do so much.”

Grassley and Thomas have already missed a Republican leadership-imposed deadline of Oct. 17 to finish the Medicare prescription drug negotiations, and many Members predicted at least another two to three weeks of intensive, daily sessions to work out the remaining trouble spots in the bill.

Plus, the two chairmen were unable to settle their disagreements over how to configure a nearly $16 billion tax-cut package for the energy bill in time for the House to bring up the energy conference report on Tuesday.

Senate Energy and Natural Resources Chairman Pete Domenici (R-N.M.) has been openly frustrated by the delay, considering that he and House Energy and Commerce Chairman Billy Tauzin (R-La.) say they have already resolved the trickiest of the nontax issues in the bill.

“They keep saying they’re close, but …” Domenici said as he shrugged his shoulders skeptically.

The policy disputes between Thomas and Grassley generally come down to differences between rural and urban interests as well as historic tensions between the prerogatives of the House and Senate.

But the two also appear to have deep personal differences, leading to a distrustful relationship that has hampered most of the negotiations the two men are required to complete as part of the Congressional conference committee process.

Just this week, Thomas instructed Grassley to stop talking to the press about the daily machinations of the Medicare conference committee. That move angered the Senator and has only further fueled Grassley’s apparent belief that Thomas is disrespectful towards his peers.

Grassley highlighted the tensions in an interview, joking that he couldn’t talk to the media. “Thomas will get me impeached,” he said.

Nevertheless, Grassley added pointedly, “I told him I’m going to talk to reporters anytime I want to talk to reporters.”

Grassley acknowledged that the friction between Thomas and himself makes finding solutions to legislative problems that much harder, though he does not let it get personal.

“There’s nobody on Capitol Hill, including Congressman Thomas, that I don’t like. So it’s not a problem for me,” said Grassley. “It’s a problem in getting my job done, but it’s not a problem for me personally. It’s just the people I have to deal with.”

Thomas spokeswoman Christin Tinsworth didn’t deny that tensions exist but said the two have always been able to, in the end, work out their differences.

“Both chairmen are legislators at heart and want to work to get a resolution, and they always get the job done,” she said.

The trouble this year also comes from the volume of “high priority” work being sent to the Ways and Means and Finance panels.

Grassley and Thomas have already successfully negotiated President Bush’s $350 billion tax cut this year, which featured Thomas storming out of the room at one point because of disagreements with Grassley. The two have also sparred over a child tax credit bill that is still unresolved.

The Medicare conference has been complicated from the beginning by clashes over who should chair the conference. And in August, after Thomas won the battle to chair the conference, Grassley ordered his aides to boycott staff-level Medicare talks because he believed Thomas was giving short shrift to his rural health care issues.

Sen. Don Nickles (R-Okla.) said the two chairmen’s disagreements often can be muted by intervention from GOP leaders, the White House and other lawmakers.

“Sometimes it helps that some others of us are able to help figure out compromises, and I think we’re doing that on the two bills,” he said.

But Sen. Max Baucus (D-Mont.) blamed an “AWOL” White House for not stepping in to mediate disputes and help lighten the committees’ load.

“A lot is in the Finance Committee,” said Baucus, the panel’s ranking member. “It just has to be managed well” by all parties.

Still on the Finance and Ways and Means plates are the welfare bill reauthorization, an employee pension measure, another potentially complicated tax cut expected to be pushed by the Bush administration next year, and a corporate tax bill already being considered.

While Congress has taken action to allow them to postpone the welfare and pension bills, which have upcoming expirations, lack of progress on the corporate tax bill could cause the European Union to move as early as this year to impose trade sanctions on the United States.

Tinsworth said Thomas was committed to getting the bill done this year before Congress adjourns. However, GOP leaders have not yet identified the bill as a must-do before adjournment. In addition, Thomas has had a difficult time selling his proposal on the corporate tax bill to fellow Republicans on the Ways and Means Committee.

Grassley was less optimistic than Thomas, noting that the corporate tax bill “should pass this year.”

“But will it pass this year? I don’t know,” said Grassley. “So then we have to count on the forbearance of the European Union not to impose sanctions. That’s a gamble.”

Lott said the Finance schedule has been “overwhelming” this year and has created a kind of legislative bottleneck.

“Part of the reason is that Finance and Ways and Means have huge jurisdictions — health, Social Security, Medicare, Medicaid, taxes, trade, foreign policy issues coming under the jurisdiction of tax and trade policy,” said Lott.

“This year, just about everything we have done, with the exception of the African AIDS bill and the FAA bill, it’s all been coming right through Finance,” he added. “And it’s just really unfortunate that there are two key people involved in all those issues — the same two — and they don’t get along very well.”