Of course, the fate of the Voting Rights Act is vitally important to the lawmakers who survive or sweat because of racial bloc politics. And the future of the Defense of Marriage Act is of keen interest to the lawmakers who see their main causes in the trenches of the culture wars.

Their suspense is about to come to an end, with rulings about the constitutionality of both laws due as soon as Tuesday morning and for sure within a week.

However, for every member of Congress, the year’s biggest Supreme Court announcement came Monday. The justices agreed to consider the “recess” argument between the Senate and President Barack Obama. It’s an admittedly arcane dispute over the president’s ability to make appointments to Cabinet offices, regulatory agencies and the courts while Congress is not in session. But it could be the most consequential balance-of-powers case to come before the court since the line-item veto was struck down 15 years ago.

The outcome — oral arguments will happen this fall and a decision would be expected within a year — could redefine legislative and executive branch prerogatives for decades.

In the short term, it will be especially important as Obama works to shape his own administration, the autonomous regulatory agencies and the federal courts during the final two lame-duck years of his second term. Regardless of whether they win back control of the Senate, Republicans are likely to be as determined as ever to limit the president’s reach after the midterm election.

The case looks to require the judicial branch to insert itself into just the sort of highly politicized disputes between the executive and legislative branches that so many judges say they want to avoid.

And, at its core, the central question looks to be little more than a question of 18th-century semantics — about the meaning of Article II, Section 2’s presidential power “to fill up all vacancies,” which normally require Senate confirmation, if they “may happen during the recess of the Senate.”

Is that whenever senators look for all the world like they’re taking a break from their business during the year? Or is it only when there’s a formalized adjournment under way between the end of one session and the start of the next?

Deciding the case one way would preserve the traditional avenue Obama and his predecessors have had around their most nettlesome confirmation fights. A decision going the opposite way would theoretically eliminate the recess appointment power entirely.

Three regional federal appeals courts have upheld the president’s customary recess appointment powers, the last time eight years ago. But two different appeals courts have rejected the practice outright this year.

The ruling the Supreme Court has now agreed to review came in January from a D.C. Circuit Court of Appeals panel of three Republican presidential appointees. The other case was decided 2-1 in May by the 3rd Circuit Court of Appeals in Philadelphia; the two judges in the majority were GOP nominees, while the dissenter was an Obama pick.

Both involved the three recess appointments Obama made in January 2012 to the National Labor Relations Board, Washington’s main forum for settling disputes between workers and management.

The partisan sheen to both rulings has inevitably given rise to talk that two centuries of precedent is being imperiled by a new generation of activist conservative judges out to reverse the activist liberalism of the past.

Those suspicions would only become more prominent if the Supreme Court rules against Obama just as the 2014 campaign is moving into high gear. If the court decides he violated the Constitution when he filled three NLRB vacancies — and when he installed Richard Cordray as head of the new Consumer Financial Protection Bureau — the ruling could also invalidate each of the hundreds of generally favorable-to-the-left decisions rendered since then by both agencies.

The plaintiff in the case is a small Pepsi bottling company, Noel Canning, which argues that an NLRB ruling against it is invalid because three commissioners were improperly seated in their posts. In theory, a ruling in favor of the bottling business could call into question the legitimacy of any decision by any official who ever got on the job with a recess appointment in the middle of the year — more than 500 since George Washington’s time, including three Cabinet secretaries, a Federal Reserve chairman, a CIA chief, 15 federal judges and a host of regulatory board members.

Senate Republicans had made quite clear they weren’t going to advance the NLRB or CFPB nominations — their way of limiting both agencies’ powers. The president announced the moves when almost all senators were back in their states for a long break over the holidays. But the GOP leadership, in an explicit bid to thwart such appointments, insisted that a “pro forma” meeting be convened every third weekday as a way to underscore that the winter break was not a recess-appointment kind of recess. The move emulated what Senate Democrats had insisted on when George W. Bush was president and felt stymied by the slow pace of confirmations.

As part of its review, the Supreme Court agreed to consider the legitimacy of such pro forma sessions. Solicitor General Donald Verrilli, in his brief asking the justices to rule on that question, argued that those meetings shouldn’t be allowed to mask reality when the Senate is shut down for all intents and purposes. When Obama acted, Verrilli noted, the unanimous consent agreement setting the Senate schedule for the first three weeks of 2012 mandated “pro forma sessions only, with no business conducted,” which in the president’s view meant the Senate said it was not available for its advice and consent role.

Minority Leader Mitch McConnell and 44 other Senate Republicans filed a brief asking the court to rule that it’s up to the Senate to decide when it’s in and when it’s not. “The chamber decided not to ‘recess,’ but instead held regular meetings, as its records attest,” they wrote. “The president’s claimed authority to name principal federal officers without the Senate’s consent while the chamber has declared itself in session has no basis in the Constitution.”

The fact that both branches of government think this is a semantic fight worth having is evidence enough of the high stakes involved.