WASHINGTON — Congress may currently look like a bit of a mess after coming to the cliff of a government shutdown and backing away, but December will be the real test for the legislature.

Both chambers are preparing to pass a clean government funding measure and send it to the president on Wednesday for his signature, hours before the Sept. 30 deadline. The problem is that the bill only includes enough money to keep the government running until Dec. 11, at which point the battles already raging in Congress will hit a fever-pitch.

With House Speaker John Boehner (R-Ohio) exiting at the end of October, the December deadline will be in the hands of new leadership — presumably current House Majority Leader Kevin McCarthy (R-Calif.), who is running to replace Boehner. If conservatives have their way, McCarthy will listen to them more than his predecessor did and take an aggressive stance on core conservative policies, forcing as many presidential vetoes as possible.

Coming out of a Republican conference meeting on Tuesday morning, lawmakers warned that with the party in flux, December could prove a nightmare. Members of the House Freedom Caucus, who edged Boehner out, will fight to have a say in the leadership scramble Boehner’s resignation has set in motion. They want a speaker who will force confrontations on must-pass bills like government-funding measures.

Conservative members plan to stake their flag in the ground when the next government funding battle starts in December, vowing to once again press whoever is the next speaker to attach provisions that strip Planned Parenthood and Obamacare funding, and restrict money from being used to implement the president’s Iran nuclear deal.

“This December is probably going to be the worst ever; I think some really bad things could happen,” Rep. Tim Huelskamp (R-Kan.), a member of the conservative Freedom Caucus, said of the next funding deadline, alluding to a possible shutdown over such controversial issues.

Huelskamp added that conservatives plan to meet with everyone running for leadership posts, and interview them to see if they meet their criteria. It’s a stunning change from the normal process, and could lead to further division within the conference.

“You just can’t change our leaders and have anything different — you have to change the process, you have to change the procedure, and that’s what we have yet to hear from those running for speaker,” Huelskamp said.

But a majority of House Republicans are upset about Boehner’s departure and the minority in their ranks sending a rift through the party.

“These guys have set impossible standards,” said Rep. Peter King (R-N.Y.) coming out of Tuesday’s meeting. “They want Obamacare repealed, it cant be done so long as President Obama is the president. I mean, their enemy is not Boehner or McConnell, it’s the Constitution.”

King expressed cautious optimism that a new speaker like McCarthy could actually solve the ever-growing problem between Republicans.

“Kevin may have the ability to smooth things over, but the factual issues are going to be the same,” King said. “They’ve set these unrealistic goals, and they condemn people for not reaching them. … We can’t have a government shutdown.”

Rep. Pete Sessions (R-Texas), who is mulling a bid for House majority whip in the leadership shuffle, also admitted to the struggle waiting for Congress in December.

“It’s going to be difficult,” he said.