An Appropriations Committee aide said a rider that would weaken new regulations on mountaintop-removal mining is a priority for House Appropriations Chairman Hal Rogers.
For instance, the Interior and environment appropriations bill , passed through the Appropriations Committee but not the full House, includes 36 separate riders on environmental issues, mostly halting or stalling Environmental Protection Agency regulations.
An Appropriations Committee aide said one of those riders, which would weaken new regulations on mountaintop-removal mining, is a priority for Rogers. But protecting the regulation is also a priority for Democrats, who see a fight on the issue as a political winner.
House Minority Whip Steny Hoyer is circulating for signatures a letter to Boehner calling on Republicans to drop riders that are "not only controversial but blatantly partisan."
The letter cites as examples provisions to strip funding for the new health care law, halt environmental regulations and alter laws on abortions.
But the letter doesn't rule out all riders, saying "not all policy riders are objectionable."
In a brief interview, the Maryland Democrat declined to say what riders Democrats might be open to, saying, "I don't want to go into specific riders."
But he described those that Democrats would fiercely oppose as "the usual riders that they put in that clearly are not out of the authorizing committee, clearly are very controversial, clearly will undermine the ability once again to reach agreement on funding the government in an orderly way so that we will give additional confidence to the country that we can operate in a bipartisan way to fund our government."
House conservatives are also gearing up for the fight.
Rep. Steve King (R-Iowa) vowed last week not to vote for the Labor, Health and Human Services, and Education appropriations bill if it funds the health care law.
"I'm not funding" the health care law, he told Roll Call. King blasted Democratic officials for objecting to the use of the word "Obamacare" on taxpayer-funded Congressional mass mailings, calling it "outrageous." He said he was looking for ways to again raise the profile of the law.
"I'm getting the sense that leadership may be poised to make some moves on Obamacare," King added.
So regardless of how substantive the conference committee is, the coming showdown on riders is still on schedule. And the balancing act for GOP leaders remains the same. If they keep conservative riders, they scare away Democratic votes. If they jettison too many, they risk losing Republicans who are already upset over overall funding levels.
Senate Minority Leader Mitch McConnell, R-Ky., carries a musket on stage as he speaks during the American Conservative Union's Conservative Political Action Conference (CPAC) at National Harbor, Md., on Thursday March 6, 2014.