Senate Majority Harry Reid and Minority Leader Mitch McConnell tangled over nominations for the second day in a row Thursday, with Reid raising the possibility of changing the filibuster rules on a simple majority vote to speed action.

“Despite the agreement we reached in January, Republican obstruction on nominees continues unabated, no different than it was the last Congress,” Reid said.

In an effort to avoid significant changes to Senate rules — in part because there were not 51 Democrats who supported such a change — the Senate agreed to modest adjustments to the filibuster rule that would be in effect for the two years of this Congress.

Reid said the agreement also included a pledge by Republicans to not filibuster nominees, except in the case of extraordinary circumstances, in return for Democrats agreeing not to change the rules on a simple majority. Historically, a change to Senate rules would require a 67-vote supermajority.

But the Nevada Democrat could maneuver to change the rules with a simple majority vote to eliminate the requirement for cloture on nominations, thus allowing confirmation of President Barack Obama’s nominees by a simple majority vote. Opponents call it the nuclear option.

“Republicans had agreed to cease the endless obstruction of presidential nominees,” Reid said. “They agreed that they would work with us to ‘schedule votes on nominees in a timely matter except in extraordinary circumstances.’

“In return for their saying that is what they would do, we agreed that we would not consider any changes to the rule outside regular order,” Reid continued. “Democrats have kept our word, we intend to keep our word, we have not altered the rule, but since we entered into the agreement Republicans have failed to hold up their end of the bargain.”

Earlier in his comments, Reid cautioned that he was not making a threat.

“These remarks I am giving here today are only in an effort to get this body to work well,” Reid said. “There is nothing sinister in what I am saying. I just want the Senate to work well.”

Republicans have opposed the nomination of Thomas E. Perez to head the Department of Labor, Gina McCarthy to lead the Environmental Protection Agency and Richard Cordray to keep running the Consumer Financial Protection Bureau. They also twice filibustered Caitlin J. Halligan of New York to be a judge on the District of Columbia Circuit Court of Appeals, most recently in March.

McConnell charged that Reid was seeking to manufacture a crisis and argued that Obama’s nominees have been approved at a quicker pace that those of President George W. Bush in his second term.

The Kentucky Republican pointed to votes this year, most of them overwhelming, to confirm the secretaries of Energy, the Interior, Treasury and State and the director of the Office of Management and Budget.

McConnell also sought unanimous consent to hold a Thursday afternoon confirmation vote on Sri Srinivasan to join the D.C. Circuit.

“I don’t know what the majority leader thinks advise and consent means,” McConnell said. “Listening to him it means, sit down, shut up, don’t ask any questions, and confirm immediately. I don’t think that is what the founding fathers had in mind.”

McConnell also charged that Reid is working behind the scenes to find the 51 votes to pursue the nuclear option on nominations.

“He’s been meeting with his members trying to get 51 votes to blow up the Senate,” McConnell said. “What I fear is that the majority leader is working his way toward breaking his word to the Senate and the American people, and blowing up this institution and making it extremely difficult for us to operate on the collegial basis that we have operated on for over 200 years.

“We need to think over how we conduct ourselves in this body,” McConnell continued. “The majority leader has a very important position. It is not only to lead the party of the majority; it is also to protect the institution. What I hear lacking in that speech is any interest whatsoever in protecting the traditions of this institution.”

McConnell said that proceeding down this path could threaten progress on bipartisan legislation, including an immigration overhaul, which is one of the president’s top priorities.

“We’ve got important issues coming down the pike,” McConnell continued. “What I hear here is, the majority leader does not want to keep his word to the Senate or to the American people, and we’ll keep that into consideration as we move forward.”

John McCain, R-Ariz., later on the Senate floor said he was concerned that opposition from some Republicans to going to conference on the budget resolution could prompt Democrats to seek to use the nuclear option.

“If we continue to block things like this and block what is the regular order, then the majority will be tempted to change the rules of the Senate,” McCain said. “That would be the most disastrous outcome that I could ever imagine.”

A group of Republicans, including Sen. Mike Lee of Utah, want binding instructions on the budget conferees so they cannot raise the debt ceiling as part of the budget resolution.

Sen. Carl Levin, D-Mich., who helped head off the rules showdown in January, said he still opposes using the nuclear option to change the Senate rules.

“The question is not whether the rule is changed,” he said. “The issue is whether or not the rule allowing debate on that question, which requires two-thirds to end the debate, is changed with the so-called nuclear option. If you do a good thing in a way which is explosive you’re going end up with more gridlock here, not less.”

Levin said he did not know whether fewer senators now agree with him since the issue was discussed at the beginning of the year.

“I don’t know. I have not done a vote count,” Levin said, adding that the group that headed off the rules showdown in January has had “very casual conversations” since then.

Levin said the move would violate two rules, one requiring 67 votes to end debate on changing the rules and the other that maintains the Senate is a continuing body and does not need to approve its rules every Congress, like the House.

“What the majority leader wants to do is get these things done. That is the goal and it is a very legitimate goal and he’s got to get these things done,” he added.

“Some people say ‘just use nuclear option on nominees,’” Levin said. “That makes it harder to get any legislation done around here even though you are not changing the filibuster rule on legislation.”