The pain isn’t over yet for House Democrats.

As Republican leaders continue hammering out details of how many Members will be assigned to each committee, House Democrats nervously anticipate major cuts from their ranks on key panels.

Their fears aren’t without reason, since Republicans have repeatedly said every committee will be trimmed in the 112th Congress.

On Tuesday morning, Speaker-designate John Boehner (Ohio) told Republican Members at a closed-door meeting that they will be held accountable for their participation on committees, meaning Members must regularly attend hearings and mark-ups, according to several GOP aides.

He warned that Members who currently sit on committees with conflicting schedules may be asked to give one up.

Leaders may also give up committee slots to make room for incoming Members, according to Republicans familiar with discussions. Majority Whip-designate Eric Cantor (Va.) said on Tuesday he would take a leave of absence from the Ways and Means Committee in order to clear the way for more Members to participate on the panel.

Traditionally, the top two leaders of the majority party have withdrawn from their slots on panels.

Outgoing Energy and Commerce Chairman Henry Waxman suggested that some rank-and-file Members on his popular panel may take a leave of absence to alleviate the need to remove them. The California Democrat is particularly concerned about the numbers because unlike some committees where many Democratic incumbents were removed by retirement or Election Day losses, his committee lost only six Members. That means 30 committee Democrats are in limbo.

“Yeah, there is a lot of nervousness about it,” said Waxman, who is expected to retain the ranking member position on the panel. “I don’t know the answer to the problem. We have to wait and see what Republicans do.”

Waxman said he hoped Republicans would remember how Democrats made accommodations for the GOP after the 2006 takeover.

“We tried to be as generous as we could,” Waxman said.

Rep. G.K. Butterfield, who is the 21st-ranking member of the Energy and Commerce Committee, said Members are concerned. If Republicans permit Democrats to have as many slots on the committee as the GOP has held during their time in the minority, it would be tough enough. But if the committee is made any smaller than that, it would be painful, he said.

“I just hope it won’t be too severe,” the North Carolina Democrat said.

Democrats on the Appropriations Committee are also concerned.

Rep. Dutch Ruppersberger, who would be the 24th-ranking member on the Appropriations Committee, said he’s bracing to lose his post, which he said would be “unfortunate.”

“It could happen,” the Maryland Democrat said. “There are about six of us” who would lose their seats if the committee ratios remained the same for Democrats as they have been for Republicans. Several Democratic appropriators lost or retired, but the committee did not lose nearly as many members as some other committees, such as Financial Services or Agriculture.

But Democrats aren’t the only Members holding their breath. The influx of new Members and promises by the GOP to shrink committees means Republicans will also have some tough decisions to make among their own.

More than 40 current Republican lawmakers and incoming freshmen have requested positions on either Ways and Means or Energy and Commerce — far more than can be accommodated since leadership has pledged to cut committee size on both sides of the aisle. Five Republicans on the Energy panel will not return this cycle, and two are gone from Ways and Means.

Whether to place members of the large freshman class on committees where few freshmen have ever set foot is also an ongoing debate behind closed doors, according to several Republicans familiar with the discussion process.

Several in the large, influential class have already been given unprecedented access to the leadership table and the Steering Committee.

For Democrats, the question of which Members prosper in a smaller committee landscape may be a matter of loyalty.

Some Democrats fear outgoing Speaker Nancy Pelosi will keep her allies on key committees and bump those who didn’t support her decision to stay in leadership. In particular, some Members have worried because the California Democrat’s closest Caucus allies, Reps. George Miller (Calif.) and Rosa DeLauro (Conn.), are expected to be named policy co-chairmen on the Steering Committee, which determines committee assignments.

But despite the talk, Rep. Jim Matheson (Utah), co-chairman of the fiscally conservative Blue Dog Coalition and a Pelosi critic, said after the midterm elections that he wasn’t worried about losing committee assignments because of Caucus politics.

And Rep. Mike Ross, who has come out strongly against Pelosi continuing in leadership, dismissed any suggestion that she might retaliate by kicking him or other foes off of their committees. The Arkansas Democrat has a prized slot on the Energy and Commerce Committee.

“Something like that’s never been done and never would be,” he said confidently.

Asked if it would be a big problem if it happened anyway, he smiled. “What do you think?”

Steven T. Dennis contributed to this report.