In most presidential elections, Supreme Court nominations are a major issue for elites and a substantial concern for significant parts of the conservative movement. Other voters usually see the future makeup of the court as a side matter, or not essential at all.
Justice Antonin Scalia's death will change this.
The issue of conservative judicial activism had already begun to take hold among liberals because of a series of fiercely ideological and precedent-shattering 5-to-4 decisions.
You read that right: After decades during which conservatives complained about "liberal judicial activism," it is now conservatives who are unabashed in undermining progressive legislation enacted by the nation's elected branches.
Scalia will be remembered fondly on the right as the brilliant exponent of the theory of "originalism," which provided a rationale — or rationalization — for decisions that usually fit conservative ideological preferences.
In 2010, Citizens United rewrote decades of precedent on Congress' power to regulate how campaigns are financed, facilitating a flood of money into elections from a small number of very wealthy Americans.
Three years later, Shelby County v. Holder ripped the heart out of the federal government's enforcement power in the Voting Rights Act.
Last week, conservatives on the court halted the implementation of President Barack Obama's Clean Power Plan, his central climate initiative.
This is merely a partial list. The court's conservatives have also regularly undercut the power of unions and the ability of citizens to wage legal battles against corporations.
Such decisions already had the potential to multiply the progressive constituencies invested in making the court an election issue, including political reformers, African-Americans, environmentalists and organized labor.
But Scalia's death means that Obama or his successor — if a Democrat — could overturn the conservative majority on the court, which could lead it to revisit many of the most troubling decisions of recent years.
Republicans did themselves no favors in the coming argument by moving in a hard political direction even before the tributes to Scalia had been published and even before the president had nominated someone: Senate Majority Leader Mitch McConnell proclaimed that no Obama nominee would be considered, period.
Republicans claimed precedent for ignoring court appointees from presidents who are on their way out the door. During Saturday's debate, Marco Rubio said that "it has been over 80 years since a lame-duck president has appointed a Supreme Court justice." Ted Cruz made a similar point.
Well. A Senate controlled by Democrats confirmed President Reagan's nomination of Anthony Kennedy, 97-0, in February 1988, an election year. By what definition was Reagan not a lame duck when he nominated Kennedy on Nov. 11, 1987?
Obama has rejected the rejectionists. He said he would name a new justice and said there would be "plenty of time ... for the Senate to fulfill its responsibility to give that person a fair hearing and a timely vote."
My hunch is that Obama will try to put the Republicans' obstructionism in sharp relief by offering a nominee who has won praise from GOP senators in the past.
Three potential candidates who fit that bill were immediately mentioned: Merrick Garland and Sri Srinivasan, both judges on the U.S. Court of Appeals for the District of Columbia, and Jane Kelly, a judge on the Eighth Circuit. (I should note that Garland is a friend of long standing.)
Whoever Obama chooses, he will try to make it hard for Republican senators — especially those struggling for re-election this year in blue or purple states — to claim that he has picked an ideologue.
An extended fight over the court would allow progressives, once and for all, to make clear that it is their conservative foes now using judicial power most aggressively.
The partisan outcome of this year's election thus just became far more important. This fall, Americans will not just be picking a new chief executive. They will be setting the course of the court of last resort for a generation.
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