WASHINGTON (AP) — The Senate's deal to avert a showdown over its internal rules and confirm several long-stalled Obama administration nominees could upend a major case at the Supreme Court, one that would test the president's power to use recess appointments to fill high-level posts.

The case is shaping up as a major clash between President Barack Obama and congressional Republicans over the power granted the president in the Constitution to make temporary appointments to fill positions that otherwise require confirmation by the Senate, but only when the Senate is in recess.

Obama had sought to overcome Senate Republicans' refusal to allow votes for nominees to the National Labor Relations Board and the new Consumer Financial Protection Bureau by making recess appointments. Two federal appeals courts have said Obama overstepped his authority because the Senate was not in recess when he acted. Those courts invalidated actions of the NLRB as a result.

The Supreme Court is set to consider one of those cases around the end of the year, involving a dispute between a Washington state bottling company and a local Teamsters union in which the NLRB sided with the union. The U.S. Circuit Court of Appeals for the District of Columbia overturned the board's ruling.

But now that the Senate is on the verge of breaking the logjam that led Obama to make the recess appointments in the first place, his administration may find its appetite diminished for a major high court case. That may be especially so because the justices have been more skeptical of Obama's Justice Department than its predecessors and the court's conservative majority has been hostile to union interests.

The administration would have to ask the court to dismiss the case, although that almost certainly would leave the appeals court decision in place. The Justice Department did not respond Tuesday to a request for comment.

The justices also might now see less urgency to decide the questions at issue — what is a recess, when must vacancies occur to be filled through recess appointments and can the president override Congress' own view of what constitutes a recess.

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In some instances, the new NLRB appointees contemplated in the Senate agreement could re-enact some of the earlier decisions, removing any potential taint. The NLRB did just that following a Supreme Court decision in 2010 that invalidated actions taken by only two members of the five-person board. One significant limitation is that the NLRB would have to get judges to relinquish cases currently in the courts.

"One key aspect of constitutional law is the notion of not deciding unnecessary questions, and it may be that the agreement today provides an avenue for the CFPB and NLRB to revisit their decisions and sidestep the constitutional questions at issue in the Supreme Court's recess appointment case," said Neal Katyal, former acting Solicitor General under Obama.

The case stems from Obama's decision to fill the three NLRB vacancies on Jan. 4, 2012, with Congress on an extended holiday break. At the same time, however, the Senate held brief, pro forma sessions every few days as part of the Republicans' explicit strategy of keeping Obama from filling vacancies through recess appointments.

If the justices ratify the lower court ruling, it would make it nearly impossible for a president to use the recess power, giving the opposition party in Congress the ability to block administration nominees indefinitely. And more than 1,600 NLRB decisions could fall in the process.

Rachel Brand, a senior lawyer with the U.S. Chamber of Commerce, said she hopes the court decides the case in favor of the bottling company. With hundreds of other legal challenges pending to NLRB decisions, Brand said it "would be a mess to re-litigate" those cases if the justices were to punt on the case before them.

The head of a think tank that is opposed to the chamber on the recess appointments issue said he also wants the high court to remain in the case and overturn what he sees as a damaging appeals court ruling. "The fact that Congress has now cleared the way for the board to be fully staffed with Senate-confirmed members in no way changes that calculus," said Douglas Kendall, president of the Congressional Accountability Center.

In addition to the two rulings against Obama recess appointees, three federal appeals courts have upheld recess appointments in previous administrations.

For all the Democratic complaints about Republican obstruction of the president and GOP anger over Obama recess appointments, the subject is acutely susceptible to changing political fortunes.

The parties' roles were reversed when a Republican president, George W. Bush, was in the White House and Democrats controlled the Senate in the final two years of his presidency. Then, Senate Majority Leader Harry Reid employed the same tactic of convening the Senate every few days to keep Bush from filling vacancies through recess appointments. Unlike Obama, Bush did not press the issue.

If the Supreme Court doesn't settle it now, the issue could arise again while Obama still is in office. Or the court could await a future president of either party facing a determined Senate opposition.