With a handful of races still rated as pure toss-ups, which party will control the Senate come January is far from certain.

But one thing is becoming clearer: No matter who is nominally in charge, chaos will reign. That’s because the 2015-17 version of the world’s most deliberative body risks being balkanized along lines that go far beyond party loyalty.

According to Senate aides and insiders, the incoming Democratic caucus will be far more liberal and aggressive than the current version. It will likely be purged of many of the red-state Democrats who won election or reelection in the Democratic wave election year of 2006 and who helped curb some of the party’s more progressive instincts on environmental legislation, gun measures, and financial regulation. Joe Manchin, a conservative Democrat from West Virginia, even tried to come to the aide of fellow red-state Democrat Mary Landrieu, who is facing a tough reelection challenge in Louisiana, by telling supporters that should she lose and Democrats retain control, Maria Cantwell, a noted environmentalist from Washington, would replace Landrieu as chairwoman of the Energy Committee.

“Depending on what happens next year, the handful of Democratic moderates left are going to be in a real struggle to have their voices heard in the caucus,” said Jim Manley, a former longtime aide to Senate Majority Leader Harry Reid.

Few progressives look forward to the prospect of a smaller Democratic caucus, especially one that loses the majority. But if there is a silver lining for activists, it will be that the candidates likely to win this November are those who have adopted a muscular, Elizabeth Warren-inspired approach; those who clung to muddled centrism will likely have lost.

“This year could show the Democratic Party that progressive populism is where the country is right now,” said T.J. Helmstetter, a spokesman for the Progressive Change Campaign Committee, which has worked to fortify the campaigns of those lawmakers who represent what it calls “the Elizabeth Warren wing of the Democratic Party.”

“That is going to be the lesson coming out of these elections: that this message doesn’t just work for America, it works for the Democratic Party,” Helmstetter said.

On the GOP side, over the last four years rank-and-file Republicans have been at turns frustrated and energized by a small, Tea Party-infused rebellion in their ranks. But the Rand Paul-Ted Cruz-Mike Lee contingent—the “wacko-birds,” as John McCain sneeringly called them—is likely to grow, as a number of soon-to-be arriving senators say they count the trio as legislative models. There is Rep. Tom Cotton, who is slightly favored to take the Arkansas seat held by Mark Pryor and whom Politico dubbed the leader of Congress’s “Hell No Caucus” hours after he was sworn in. There is Jodi Ernst, who has a better than even chance of winning the Senate seat in Iowa and has called federal minimum wage laws “ridiculous” and suggested that President Obama should be impeached. And then there is Ben Sasse, an all but certain winner in Nebraska who has grassroots conservatives most excited and who has already been dubbed by Slate “the next Ted Cruz.”

But if the Cruz-Paul-Lee coalition grows, so too will a countervailing force inside the GOP caucus: the sitting Republican senators who have faced a Tea Party challenger and emerged victorious. So far, it is a small group, including just McCain, Lisa Murkowski of Alaska, and Orrin Hatch of Utah. But the three have been some of the most vocal critics of the direction their Tea Party-backed colleagues want to take the party. And come January, they could be joined by 11 other Republicans who this year beat back challenges on their right flank, including Republican Leader Mitch McConnell and his No. 2, Minority Whip John Cornyn.

“I think you are going to see a lot less energy on the Ted Cruz-Rand Paul side of things, especially if we get the majority,” said one senior Republican aide. “We are going to need to govern, and everybody knows that. McConnell will get to be the true leader again.”

The multi-front battle on the GOP side is likely to grow even more heated as at least a half-dozen Republican senators use the Senate to launch their presidential campaigns. If the Cruzes and Pauls of the world had little reason to compromise before, now they will resist it completely as they seek to appeal to conservatives in Iowa and South Carolina. The more mainstream Republicans, meanwhile, senators like Rob Portman of Ohio and Florida’s Marco Rubio, will decide whether to try to out-Tea Party their colleagues or make their play as moderate lawmakers who can build bridges across the party.

“I am looking for guys who can be bold, who can really step up,” said Adam Brandon, executive vice president of FreedomWorks, the Koch brothers-affiliated group that helped foment the Tea Party revolution. “Legislatively, we will be in a better position than we have been in a while.”

Brandon dismissed the notion that the members of the establishment GOP will become emboldened after defeating right-wing primary challenges.

“The lesson of this year is that it is very hard to keep the chamber if you don’t have grassroots conservatives behind you,” he said. “Are they really going to keep spending tons of money to keep these seats?”

If an emboldened Democratic caucus and a GOP split between a loud and growing Tea Party wing and a vengeful establishment wing were not enough to make the U.S. Senate seem like the student government at Faber College, consider this: Next year’s chamber also could feature the largest ever group of independents who proclaim allegiance to neither party.

Sen. Angus King, the independent from Maine who caucuses with the Democrats but has said he could flip Republican if they take over control, could be joined by Larry Pressler of South Dakota and Greg Orman of Kansas, both of whom lean left but whose loyalty could be up for grabs. If the three become the difference for either party between winning or losing control of the chamber, some Senate watchers fear they will switch between the two sides depending on who can offer the sweeter deal.

“Any one of them could theoretically change the conversation about what it takes to get something done in the Senate,” said Evan Bayh, himself a two-term centrist Democrat from Indiana. “But you run the very real risk of being little more than an interesting gadfly.”

And of course, as Bayh and others pointed out, this is the U.S. Senate, a body where someone standing up and talking for a very long time is among the most exciting gestures possible and where 60 votes is still required to take any meaningful action.

“The best hope [for getting something done] is the growing job dissatisfaction that many members feel,” he said. “There are a lot of people who ask themselves, ‘Why am I here if nothing gets done?’ There is has to be something beyond ideological fights that go nowhere.”