Everybody’s got the bomb, we can all die any day. Photo: AFP/Getty Images

The Senate just passed a rule change that, on its face, makes very little sense. By a 52 to 48 margin, senators — all Democrats — voted to eliminate filibusters of judicial and executive-branch appointments. The filibuster still exists for regular legislation and Supreme Court appointments.

Lowering the threshold for executive-branch appointments makes perfect sense — presidents ought to get wide discretion to fill out their own team. But why the ban on judges rather than legislation? Legislation can always be overturned, while judges sit on the bench for life. And why the exception for the Supreme Court?

The main reason for this odd, partial clawback of the filibuster is that President Obama has no real legislative agenda that can pass Congress. At the beginning of the year, it seemed plausible that House Republicans might go along with immigration reform, but even that possibility now looks remote. Nothing can pass.

That reality means two things. The first is that President Obama’s second-term agenda runs not through Congress but through his own administrative agencies. His appointees are writing rules for financial reform, housing policy and — the potentially enormous one — climate emissions. Senate Republicans have tried to stymie this agenda by blocking executive-branch appointments, most recently filibustering the nomination of Mel Watt to run the Federal Housing Finance Agency. The executive-branch filibuster has become a primary Republican weapon against Obama’s agenda.

Their next line of defense is the D.C. Circuit, the federal court that handles regulatory cases. If and when the Environmental Protection Agency issues regulations on existing power plants, the D.C. Circuit will rule on their legality. Republicans had announced their intention to block any Obama appointment at all to the court’s three vacant positions in order to protect their party’s functional majority. (The court is currently split evenly, but it sends its overflow caseload to retired judges, who are mostly Republican.) The D.C. Circuit is where Republicans had hoped to block those parts of Obama’s executive agenda they couldn’t gum up by denying the agencies a functioning director.

Senate Democrats changed the rules because they felt burned by Republicans. In 2005, Senate Republicans threatened to carry out the same nuclear rules change, and Democrats backed down. One of the judges Democrats agreed to let through, Janice Rogers Brown, holds radical libertarian beliefs, and just struck down Obama’s birth-control-insurance mandate. The double standard in which a Republican president can seat a Janice Rogers Brown and a Democratic president can’t even seat moderates judges with bipartisan support like Patricia Millett became too galling for Democrats to stand.

The longtime counter-threat against the “nuclear option” has always been that the minority party will retaliate by wantonly blocking everything that passes through the Senate. But here is the second way in which the end of Obama’s legislative agenda has forced the nuclear confrontation. With immigration reform dead, or nearly dead, the Senate Republican retaliation amounts to threatening to burn down a building that is already in ashes.

The final oddity is the exception for the Supreme Court. Democrats have supposedly granted the principle that Republicans can filibuster a potential Democratic nominee. The agreement will probably hold if Democrats replace one of the four Democratic-appointed justices.

But what if one of the five Republican-appointed justices retires (or, more likely, dies) while Obama or a successor Democrat holds the White House? Will Republicans really stand by and allow that president to flip the Court’s majority? Or will they use the same logic they are using with the D.C. Circuit, arguing that the current ideological balance of the Court must be preserved? The pressure from social conservatives to hold a filibuster would be immense. And then, in all likelihood, the nuclear option will be triggered again.