Fights over nominations have begun to dominate the Senate’s agenda as both parties look for places to one-up each other in a chamber with little else to do.

Republicans last week threatened to block President Barack Obama’s nominees as a way to gain leverage on other issues. Meanwhile, Senate Majority Leader Harry Reid (D-Nev.) shifted chamber action to several of the White House’s more controversial nominees after spending five fruitless weeks of floor time on a small-business bill.

Aides to both parties said the nominating process is still working better than it did in the past Congress. In fact, the pace for approving judges has improved this year following a gentlemen’s agreement between Reid and Minority Leader Mitch McConnell (R-Ky.) and a subsequent bipartisan deal to reduce the number of appointments that need Senate confirmation.

But taking nominees hostage is still a popular pastime.

Obama hasn’t even nominated a director for the controversial new Consumer Financial Protection Bureau, but 44 Republicans sent a pre-emptive missive to the White House on Thursday vowing to block anyone he chooses. Only 41 votes are needed to filibuster a nominee.

The letter, signed by all but two GOP Senators, demanded that Obama make “structural changes … to hold the Bureau more accountable to the American people.” Another demand is to replace the director position with a board. The threat essentially seeks to serve as a rematch over last year’s regulatory reform battle, with the Republican Senators trying to limit the new bureau’s sweeping powers — and probably ensuring that the post will be filled by a recess appointment that bypasses the Senate entirely.

Republicans also applied the same tactic last week to a brewing fight over a ruling by the National Labor Relations Board against the Boeing Co.’s plans to open up a non-union airline plant in South Carolina.

Nineteen Republican Senators led by Sen. Jim DeMint (S.C.) wrote to Obama and vowed to use every procedural tool at their disposal to block the  confirmations of Craig Becker to the board and Lafe Solomon as the board’s general counsel.

“Successful workers rights are being stamped out by political appointees who serve at your pleasure and have not been confirmed by the Senate,” they wrote. They complained that Obama had installed labor lawyer Becker with a recess appointment even though 41 Republican Senators sent him a letter urging him not to do so.

“The Senate has been unacceptably denied the ability to exercise its constitutional duty,” they said. The president is permitted to appoint temporary custodians when Congress takes long recesses, but the practice often stokes partisan ire in the Capitol.

Earlier this year, McConnell threatened to block all of Obama’s trade nominations until the president sends to Congress all three pending trade agreements — South Korea, Panama and Colombia.

That threat appears to be bearing fruit. The administration announced last week that it is moving forward on completing all three.

Reid, meanwhile, has moved on from the small-business bill, which had become a pincushion for weeks for unrelated amendments. It ultimately foundered over Small Business and Entrepreneurship ranking member Olympia Snowe’s (R-Maine) demand for a vote on a sweeping regulatory reform amendment that Democrats believe is politically radioactive.

Last week, Reid beat back a filibuster attempt against — and ultimately won confirmation for — the nomination of John McConnell as a district court judge in Rhode Island. Republicans had held up the nomination for more than two years.

Reid also scheduled a vote on the nomination of Jim Cole as deputy attorney general for today. Cole is already serving via a recess appointment and handles national security issues ­— a point Reid pressed publicly last week after the killing of terrorist mastermind Osama bin Laden. Cole was first nominated a year ago. Next up will be the nomination of Ed Chen to a district court judgeship in California.

“We would like for all the president’s nominees to be given a timely up-or-down vote,” Reid spokesman Jon Summers said. “That said, nobody expected parties to completely abandon the procedural options available to them, or for us to abandon our attempts to confirm the president’s well-qualified nominees.”

Republicans last week grumbled that plenty of noncontroversial nominees are lined up and ready to go, but that Reid has chosen to push through more controversial ones, such as John McConnell, first.

“We have been working in good faith with our Democrat colleagues to confirm consensus judicial nominees in general and to fill judicial emergencies in particular,” Mitch McConnell complained. “So it is disappointing that our Democrat friends have chosen to depart from this bipartisan practice and to press the McConnell nomination, which would not fill a judicial emergency and is about as far from a consensus nomination as one could imagine.”

The Kentucky Republican also said that while he has in the past opposed the filibustering of district court nominations, Democrats pioneered the practice when Republicans held the presidency and now have to live with the precedent.

He voted to block last week’s judicial pick, but the nomination moved forward anyway.

Republicans also pointed to the resumption of fights over nominations as a sign of the Senate’s light workload so far this year.

“They have nothing else to put on the floor so they have to resort to nominations,” said a GOP aide, who called the agenda “pathetic.”

But Democrats have complained that the GOP has obstructed passage of relatively noncontroversial items such as the small-business bill.

The partisan sniping, meanwhile, should resume next week, with Reid likely to bring a bill to the floor nixing oil company subsidies. An extension of the USA PATRIOT Act is also due. But the big decision for Reid is whether to bring a Democrat-only budget resolution to the floor or to wait for a bipartisan group headed by Vice President Joseph Biden to reach an agreement on a broader deal to raise the federal debt limit.