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President Obama is planning to nominate three judges to the United States Court of Appeals for the District of Columbia, reports Michael Shear. The D.C. Court of Appeals has, over the last decade, become a pivotal institution whose importance, unbeknownst to even many close followers of politics, now approaches that of the Supreme Court or Congress. Obama is provoking (or, more accurately, joining) a conflict whose outcome will shape his second term in nearly every facet, but especially his administration’s chance of completing its climate-change agenda.

The court is a flashpoint where two distinct streams of the partisan wars converge. The first is legal. Since the second term of the Bush administration, conservatives have increasingly despaired of the prospects of passing their agenda through elected channels and embraced a radical legal vision some of them call “The Constitution in Exile.”

For most of the postwar years, conservative jurists defined their mission in mostly defensive terms. They wanted to prevent liberal judges from activist rulings that created new judicial rights, like those created in Brown v. Board of Education, Miranda v. Arizona, and Roe v. Wade. The Constitution in Exile movement seeks to get conservative jurists out of their defensive crouch and onto the offensive. Its aim is to restore the courts to their role before 1937, when they were controlled by arch-conservatives who interpreted the Constitution (much as the tea party does) to forbid extensive government regulation of the economy.

The movement’s highest-profile effort has been the unexpected and nearly successful legal challenge to Obamacare, a form of economic regulation whose constitutionality would not, not long ago, have been considered not remotely questionable. But the movement has also struck a series of powerful blows at the regulatory state, and those victories have taken place in the D.C. Circuit. Federal appeals courts are divided up by territory, and since the D.C. Court of Appeals covers challenges filed within the District of Columbia, which is where one would challenge laws passed by Congress, it has an outsize role. In recent years, the D.C. Circuit has become a kind of mini–Supreme Court, and its conservative majority has struck down a wide array of regulations on Wall Street, labor, the environment, and others.

If Obama can change the partisan balance of the court, he can dramatically curtail what has become one of the conservative movement’s most powerful weapons. If his administration follows through on its anticipated plan to regulate power plants through the Environmental Protection Agency, conservatives will challenge the regulations, and the challenge will run through the D.C. Circuit. So the outcome of the court fight will determine not only sundry political questions but quite possibly also Obama’s last shot to prevent catastrophic climate change.

But the D.C. Circuit fight has other ramifications for Obama’s second term — it is the battleground the administration is choosing for a broader confrontation over the Senate filibuster as a tool of massive and unprecedented obstruction.

This is a fight that also dates back a decade. In 2005, when Democratic senators filibustered George W. Bush’s court nominees, the Republican Senate threatened to ban all filibusters on judicial nominations, a move both sides called “the nuclear option.” Democrats persuaded Republicans not to change the rules by agreeing to an informal principle that they would only filibuster judges in “extraordinary circumstances.”

That threshold turned out, in practice, to be so high as to be essentially nonexistent, as Democrats acceded to the appointment of all of Bush’s nominees, including Janice Rogers Brown, a tea-party-style legal activist given to ranting about the New Deal and communism. Those Bush nominees gave the D.C. Circuit its current conservative majority.

Since then, Democrats have regained the Senate majority, and Republicans have not only replicated the Democrats’ filibuster tactics but surpassed them. They have filibustered Caitlin Halligan, an Obama nominee for the court, because, as a solicitor general in New York, she litigated a class action lawsuit against gun manufacturers — which is to say, they have defined “extraordinary circumstances” as disagreeing with a single ruling, a standard of rejection far lower than the one Senate Democrats accepted under Bush.

But this is in keeping with the expanded use of the filibuster under Obama. All of the old informal social norms that once curtailed its use have given way. Senate Republicans have begun using the filibuster against Obama’s appointments to his own administration, threatening to block any nominee unless Obama agrees to weaken laws Republicans don’t like. They have, for instance, hobbled the Consumer Financial Protection Bureau by preventing the confirmation of any nominee at all. This is an astonishing new power that has allowed Senate Republicans to overturn a fight they seemed to have lost when Congress passed the Dodd-Frank financial reform in 2010. Brookings scholar Thomas Mann has called this new tactic “nullification” — the use of extraordinary threats by a legislative minority to prevent duly passed laws from being carried out. Harry Reid has recently threatened to change the rules of the Senate to prevent any filibusters of judicial or executive branch nominees. (Reid’s rule change would not stop the minority from blocking new laws, only new appointments.)

Obama’s troika of appointments to the D.C. Circuit — Cornelia T. L. Pillard, David C. Frederick, and Patricia Ann Millett — are designed to trigger this threat. Obama has selected the most favorable ground on which to hold the fight. Senate Republicans at least claim that they are abiding by the “extraordinary circumstances” standard for rejecting appointments. When they filibustered Halligan, they described her gun lawsuit ruling as so extraordinary as to justify a filibuster, even though it would be preposterous to assert that Halligan is more extreme than a Janice Rogers Brown.

Obama is calculating that, by making three selections at once, Republicans in the Senate won’t be able to use the same pretense they used against Halligan — picking out one objectionable ruling and calling it an extraordinary circumstance. To block all three nominees would be to find three different extraordinary circumstances at once. It would essentially force them either to confirm the troika or admit that their real policy is to block any Democratic nominees to the court, which would trigger Reid’s threat to change the rules. If Reid actually pulled off the rule change, it would flip the entire Obama second-term dynamic. The biggest impediment to regulating climate change would disappear, as would the GOP’s ability to bottle up the regular functioning of his administration. I wrote a print story in February arguing that the central conflict of Obama’s second term is the tension between his emerging popular majority and the continued ability of Republicans to exert power without appealing to a majority. The court nomination fight strikes directly at the heart of two of those power channels — the filibuster and the Constitution in Exile movement.

None of this is to say that Obama’s gambit will work. Senate Republicans will have the next move. They may confirm the three nominees and head off Reid’s threat to limit the filibuster. Or they may stall or split them apart or refuse outright, perhaps gambling that Reid can’t actually muster 50 votes to change the Senate’s rules. The smart Republican play may be to compromise on the judges, thereby heading off the nuclear option threat, but that would give Obama the victory of filling vacancies in the court that will likely rule on the biggest piece of his second-term agenda.

But Obama has made a strong opening move here. Senate Republicans have enjoyed so much success bottling up his nomination not only because they have seized unprecedented new powers, but also because Obama has done so little to challenge them until now. The Senate Republicans have in a sense filled a power vacuum caused by Obama’s inattention. They may well hold on to that power, but now, it seems, they’ll have to fight for it.

Update: The first version of this post incorrectly described Caitlin Halligan’s relationship to a lawsuit against gun manufacturers. She litigated it as solicitor general, she did not rule on it, which makes the opposition to her all the more unjustifiable.