Long-simmering tensions between Senate Majority Leader Harry Reid (D-Nev.) and Sen. Tom Coburn (R-Okla.) could boil over on the floor as early as this week, with Reid planning to bring a stalled public lands bill to the floor — despite accusations from Coburn and Senate Minority Leader Mitch McConnell (R-Ky.) that doing so would break an agreement between Coburn and Reid.

Since taking control of the Senate in 2006, Democrats have become increasingly frustrated with Coburn, who has used the chamber’s rules to either block bills or exact significant changes from Democrats.

The last straw for Reid came earlier this year. A unanimous consent deal he and Coburn struck Dec. 19 permitted Coburn up to five “relevant” amendments to the bill. Coburn filed seven possible amendments to the public lands package that included several politically charged provisions, such as one to allow guns in national parks.

In the deal, neither side specified the nature of the amendments, though Reid assumed Coburn would move forward with offset amendments because the Oklahoma conservative had publicly criticized the bill for its costs.

In response to the seven possible amendments Coburn filed, Reid refiled an exact copy of the package of 62 land bills under a new bill number, a procedural tactic that allows him to break the underlying agreement of the unanimous consent deal without violating the UC itself. Democrats angrily accused Coburn of negotiating with Reid in bad faith by considering amendments outside the scope of costs.

With Reid preparing to finally force the issue as early as week’s end, Coburn is finding defenders, including those such as McConnell, who often find themselves on the opposite end of Coburn’s procedural machinations.

“The fundamental issue here is that Sen. Coburn felt strongly that he had an agreement and that it was not being honored,” McConnell said.

McConnell added he has discussed Reid’s treatment of Coburn with GOP colleagues.

“I’ve made it clear that I feel Sen. Coburn was treated unfairly,” McConnell said. He also said that when Reid brings the new bill up for consideration, he will be shoulder-to-shoulder with Coburn on the floor. “I think it’s important for me to stand with my colleague,” McConnell said.

McConnell declined to say whether he would whip the vote as a “procedural” measure — which would mean he was setting a Conference position for the vote — or work more informally to support Coburn. But Republicans said McConnell took part of last Tuesday’s weekly Conference luncheon to talk about the issue with the Conference and made the case that regardless of the bill’s merits, Reid overstepped his bounds, and the issue was one of protecting the rights of the minority rather than Coburn’s position on the bill.

McConnell has also discussed the issue with Minority Whip Jon Kyl (R-Ariz.) and other leaders, Republican aides said.

Coburn spokesman John Hart rejected the argument that the Senator has acted in bad faith and laid the blame for the latest dust-up at Reid’s feet. “It’s very simple. The UC agreement Majority Leader Reid put into the record reflects the UC agreement Sen. Reid personally made with Dr. Coburn. If the Majority Leader can’t be trusted to honor UC agreements, Dr. Coburn, and other Senators, may simply refuse to grant any such requests. As a result, bills that could pass in minutes or hours will instead take days or weeks to consider,” Hart said.

Wary of his ability to employ the chamber’s arcane procedural rules to tie the Senate in knots, Democrats have not publicly criticized Coburn. But privately they complain he and his staff have manipulated the Senate’s rules for what they see as partisan goals, such as forcing Democrats to vote on the politically painful gun amendment.

Democrats said the public lands fight is part of Coburn’s broader pattern of using the chamber’s rules in bad faith to slow work on bills. They contend he has no interest in actually moving legislation.

At the committee level, Democrats and Republicans said Coburn has become adept at using procedural rules to bring legislative activity to a near standstill.

For instance, over the last year Coburn has entered protracted negotiations on a host of bills ranging from an ALS registry bill to legislation banning discrimination in health insurance policy decisions based on genetic issues.

In each case, Coburn or his staff would identify problems with the bill, enter into talks with Democrats — and in some cases Republicans as well — that would last several weeks. At the end of negotiations, Coburn or his staff would then present a new set of issues with the bill — prompting more negotiations.

In the case of the public lands measure, Energy and Natural Resources Committee Chairman Jeff Bingaman (D-N.M.) said he and Coburn discussed the package of bills several months ago, and he never raised any issue outside the added spending. “When I spoke to Sen. Coburn ... he said his concern with these bills was that they were authorizing a lot of new spending,” Bingaman said.

While Bingaman offered to allow votes on amendments to offset the cost, Coburn declined because he did not want to be limited to the offset issue.

Bingaman, who was not involved in the UC agreement between Reid and Coburn, said negotiations essentially ended until the late December deal that prompted the UC.

On the floor, Coburn has been more direct in his efforts, simply placing holds on bills that he finds objectionable. And, Republicans point out, he has often been easy for Democrats to work with, with one source pointing to the deal cut between Coburn and Sen. Charles Schumer (D-N.Y.) late last year to move mortgage legislation that essentially gave Coburn time on the floor to debate the bill before its passage.

Nevertheless, Democrats complain that the Senate should not be subject to the whims of one Member.

Reid spokesman Jim Manley argued that while “he’s got every right to use all the tools to try and block legislation ... at some point enough is enough,” and said McConnell ultimately is responsible for reining in Coburn to ensure the chamber operates smoothly.

“The question is whether the Republican leadership is going to let one or two rogue Members” hold the chamber hostage, Manley said, arguing that Coburn “went too far and his colleagues, and ultimately their constituents, will be the ones to suffer” if progress continues to be hampered.

Republicans, however, warn Coburn is a shrewd legislator and made it a point to learn the chamber’s rules when he entered the Senate.

“Most Democrats stereotype Coburn as unschooled when they first meet him. But those who continue to think that, after working with him for a while, ought to be ashamed of themselves for ever having [done so], and this incident should remind them not to fall victim to their stereotypes,” one former GOP leadership aide said.