Two leading advocates of overhauling the Senate’s filibuster rules put the decision about the size and scope of the package squarely in Senate Majority Leader Harry Reid’s court Thursday afternoon.

But whatever changes to Senate rules the Nevada Democrat decides to pursue, Democratic Sens. Jeff Merkley of Oregon and Tom Udall of New Mexico told reporters they expect any package would garner the votes need to move on the floor, either using the constitutional or nuclear option of changing the rules with a simple majority or a bipartisan deal with a higher threshold.

“Most serious reforms of the rules occur because a leader has 51 votes behind them, and that’s where Harry is now,” Merkley told reporters. “That is what enables him to negotiate. On the other hand, if the negotiations succeed … that’s great. It would be wonderful to have a bipartisan agreement.”

“I think he has a real instinct as to what will make this place work better, and so I’m of the opinion that when he gets to that final point,” the caucus will back him up with at least 51 votes, Udall said.

Merkley added that the attempt at negotiations between Reid and Minority Leader Mitch McConnell, R-Ky., would strengthen the Democratic hand if the caucus decided to move forward without GOP support. Reid said Thursday he was already meeting with his Republican counterpart on the issue.

“Striving to be more productive will do little if we do not address the major reason for our inefficiency. The Senate is simply not working as it should. That is why, in the last Congress, I made plain that Democrats would do something to fix these issues,” Reid said, expressing optimism the two leaders would reach an agreement.

The reform-minded senators have questioned McConnell’s position, however. Merkley criticized McConnell’s opposition to the “talking filibuster” that would require senators to stay on the floor if they oppose a measure.

“The fact that he is so opposed to folks having to making their case before their colleagues and the American people is just a direct commentary on the current use of the filibuster as a device of paralysis, not a device of deliberation,” Merkley said.

Merkley and Udall are trying to ensure any Senate rules overhaul includes a way to force senators on the floor to actually debate legislation, which is vociferously opposed by Senate Republicans because it would eliminate the automatic 60 vote requirement for moving legislation in the face of filibuster.

“We will reserve the right of all senators to propose changes to the Senate rules. And we will explicitly not acquiesce in the carrying over of all the rules from the last Congress,” Reid said on the floor. “It is my intention that the Senate will recess today, rather than adjourn, to continue the same legislative day and allow this important rules discussion to continue later this month.”

That debate is expected to resume Jan. 22, following the presidential inauguration ceremony on Jan. 21.

Several other Democrats, including veteran Sens. Tom Harkin of Iowa and Frank R. Lautenberg of New Jersey, reintroduced their own proposals for modifying the Senate’s rules Thursday.

Harkin, for instance, is trying to revive a previously unsuccessful proposal he first offered in 1995 that would gradually reduce the threshold for cloture to a simple majority.

“I am not afraid of democracy, and my colleagues should not be afraid either,” Harkin said. “Issues of public policy should be decided at the ballot box, not by manipulation of arcane procedural rules. After ample protections for debate, deliberation and amendments, the majority in the Senate should be allowed to carry out its agenda, to govern, and to be held accountable by the voters.”

At the end of the day, however, the responsibility for action rests with Reid.

“This is going to be a judgement call on his part as to whether or not this is a substantial package, whether it’s a bipartisan package or one that he has to do individually,” Udall said. “But I think he’s going to push for what he believes is the … strongest proposal he can get.”