Senators say they are ready for what Majority Leader Mitch McConnell plans to give them this week: a return to regular order.

But that does not mean it will be easy.

The Senate is preparing to launch what is expected to be a bruising and at-times bitterly partisan deliberation on the future of a program that covers the so-called Dreamers, young undocumented immigrants brought to the country as children.

The chamber will take the first step Monday to proceed to a floor debate on how to address the pending expiration of the Deferred Action for Childhood Arrivals, or DACA, program, which protects Dreamers from deportation. President Donald Trump has set a March 5 deadline for the program to end.

McConnell, a Kentucky Republican, has pledged to launch the DACA debate on a clean playing field: an unrelated bill that has no underlying immigration policy in it.

Watch: McConnell, Schumer Announce They’ve Reached Budget Agreement

While members praised the “neutral” approach, some Republicans criticized the decision not to use a base bill that reflects more conservative priorities.

“When you are in the majority, you ought to set the agenda. Which means you ought to be setting what the base bill is. To abdicate that just doesn’t seem like the right approach,” said Wisconsin Sen. Ron Johnson, the chairman of the Homeland Security and Governmental Affairs Committee.

Heading into this week, lawmakers were unsure exactly what the process would look like, including what kind of time agreement would be placed on the debate and whether McConnell would allow members to offer unlimited amendments, similar to the Senate’s voting marathons last year. Such a process would require consent from the chamber as a whole.

While members are expected to float several serious proposals — such as legislation from Arizona Republican John McCain and Delaware Democrat Chris Coons — those could be overshadowed by partisan measures intended to serve as so-called messaging bills.

“You know it’s an election year? It’s going to be full of messaging amendments. There’ll be more messaging amendments than substantive amendments,” Missouri Sen. Claire McCaskill said. “The majority of amendments that’ll be offered will have no chance of passage.”

McCaskill is arguably the most vulnerable Democratic incumbent this year.

A return to order

The DACA debate will present senators with a relatively unfamiliar approach to a floor vote — no one has any idea what the end product will look like.

“That’s the interesting thing about regular order. When you move into that, you can only directionally have a view of where you want to go. The process is gonna take you where 60 votes can take you,” North Carolina GOP Sen. Thom Tillis said.

Regular order refers to the rules and customs that make for an orderly and deliberative policymaking process. This stands in stark contrast to the past year, when the two major bills taken up by the Senate — the tax overhaul and an attempt to repeal and replace the 2010 health care law — were heavily influenced by McConnell’s office.

“There will be tough votes that we have to take, but we have to get back to some form of transparency and open and regular order,” Iowa Republican Joni Ernst said.

Watch: David Hawkings’ Whiteboard — What is Regular Order?

For newer members, such as Democrats Doug Jones of Alabama and Kamala Harris of California, this will be their first glimmer at regular order, a process not too familiar to most junior senators.

“It’s a whole new experience for me,” Jones said. “I’m just kind of looking and talking to other folks who have done it before. There’s not as many people here who have gone through it.”

But the upcoming DACA debate will not be a true return to regular order. No bill advanced through the Senate Judiciary Committee, an increasingly common trend in the chamber.

“This is regular order-lite. It’s an episodic example of regular order,” Tillis said.

Instead, members have engaged for weeks in a hodgepodge of ad hoc working groups to try to develop some sort of consensus heading into the floor action. Lawmakers who have taken an active role in those groups could introduce their own proposals.

“There’s not an agreement to say everyone on this group is on board with this and there’s not even agreement that there will only be one proposal. There may be several,” Sen. James Lankford said. “The conversation is, let’s get some things on paper and then everyone can say whether they agree or disagree.”

The Oklahoma Republican is a member of the self-describe Common Sense Coalition, a bipartisan group of senators who have been meeting since the January shutdown to try to come up with an immigration solution.

“There’s not a sense of consensus to say everyone’s on the same page on all the issues,” he said.

A hard fight

It is possible that some members will introduce legislation based on the framework released by the White House last month. That plan — which would provide a path to citizenship for many undocumented immigrants but would also include dramatic cuts to legal immigration — was rejected by both Democrats and House conservatives.

The DACA debate promises to be a grueling battle, one that members hope yields some sort of bipartisan compromise in the end.

“It’s what we used to do all the time. It’s actually fun to legislate,” Maine Republican Susan Collins said, overhearing a separate Roll Call interview.

“People are going to have to work hard to get 60 votes for their amendments,” McCaskill said.

“Very hard,” Collins added.

Lawmakers say the issue, which is historically contentious and evokes a wide variety of passionate viewpoints, has also served to bring a renewed sense of bipartisan spirit, even among the most strident opponents.

But while the Senate is set to return, at least momentarily, to a resemblance of regular order, not everyone is dusting off their rule books to study procedure.

“I’ve read a lot about the rules but I will tell you most of them seem to have been written right about the time of Moses and nobody completely understands them,” Louisiana Republican Sen. John Kennedy said.

Niels Lesniewski contributed to this report.