WASHINGTON >> Senate Majority Leader Harry Reid of Nevada knew he would anger Republicans when he threatened to change the rules of the Senate to make it harder for the minority to gum up legislation. But he is also running into resistance from fellow Democrats about the way those rules would be changed — essentially by ramming the changes through with 51 votes, rather than with the agreement of two-thirds of the Senate, which is how rule changes are meant to be made.

“I am very leery about changes to rules, except by the use of the rules,” said Sen. Carl Levin, D-Mich., “and the rules require two-thirds of votes to change the rules. I prefer not to use a mechanism which I believe is dubious.”

For several years, Republicans have repeatedly pulled out a once rarely used weapon from the procedural arsenal — the filibuster — to eat up time on the Senate floor and stall or kill legislation offered by Democrats.

Reid is not seeking to end the filibuster entirely. Rather, he wants to prevent it from being used to prevent debates on bills, to block conference negotiations between the House and the Senate on legislation, and to force senators who long to filibuster to do it the old-fashioned way: by standing on the floor talking on and on, rather than by voting with colleagues to prevent debate and then skedaddling out of town.

Because Republicans are united in their dislike of the proposed changes, Reid would never get 67 votes — two-thirds of the Senate — to break a filibuster on the filibuster change. So he could instead avail himself of a controversial option that some proponents believe is available only on the first day of a new Congress and change those rules via majority rule, or 51 votes. Opponents insist that such a move would violate Senate rules.

A majority of Democrats, frustrated by what they say is the consistent and brazen abuse of the filibuster by Republicans, appear to support changes to the rules, and some believe they do not go far enough. But others, deeply aware that a majority party today can be the sad and lonely minority tomorrow, are not keen on playing the “nuclear option” card, with majority rule.

“I don’t like the nuclear option,” said Sen. Bill Nelson, D-Fla. “I reserve the right to decide later, but instinctively I don’t like it. It’s avoiding the rules.” Nelson added that “a body like this runs on comity and common sense,” and he said he worried that going nuclear would do serious damage to that atmosphere.

The divide exists somewhat along electoral generational lines. Newer senators, appalled by the molasseslike movement of bills and the overall dysfunction of the chamber, have been urging Reid to make the changes. Sen. Tom Udall of New Mexico, who took office in 2009, has been especially ardent, though he gets a great deal of support from Sen. Tom Harkin of Iowa, who has been laboring against the filibuster for decades.

Harkin said he was not confident that the Democrats had the votes they needed to jam the changes through. “There are some Democrats who don’t want to change the way we do things around here,” he said. Other Democrats said that while they did not believe the votes were secure, they felt certain that their colleagues would come along if Republicans and Democrats could not come to an accommodation by the end of the year.

“I am an enthusiastic supporter of this,” said Sen. Barbara Mikulski, D-Md., reflecting the views of many Democrats. “There should always be the protection of minority rights, but at some point you have to show up or shut up.”

Not all Democrats are as adamant. “I am 100 percent in support of the changes,” said Sen. Claire McCaskill of Missouri. “I am not 100 percent in support of the methods. I think it is healthy that there are mixed feelings on this. We are playing with nitroglycerin here. The minority needs to respect that.”

The refusal to stomp on the will of the minority is one of the greatest differences between the Senate and the House, where the majority simply rules. Many senators in both parties agree that comity will be damaged if a 51-vote rule change comes to pass. Sen. Mitch McConnell of Kentucky, the Republican leader, has been nearly apoplectic about the issue on the Senate floor this week.

Consistently tossing back Reid’s words from previous years — in which he defended the Senate rules process — McConnell railed against the proposed changes over and over again. “I’m just perplexed about the judgment on display here,” he said, “blowing up the Senate at a time when the election is behind us.”

But Democrats argue that the filibuster has been increasingly used to block routine nominations, hold up Senate business and generally infuriate the majority, and that the rules must be tightened.

“The Judiciary Committee unanimously approves judges, yet those nominations come to the floor and we have people using a filibuster,” said Sen. Daniel Inouye of Hawaii, whose first floor speech in 1963 was in support of the filibuster. “Once the filibuster is finished, we vote almost unanimously to approve the nomination. Now what kind of playground game is that?”

Inouye stopped short of offering his full support to Reid’s plan, adding that he was “studying it.”