by Doug Kendall, President, Constitutional Accountability Center

While today the political world rushes to speculate about who will replace Justice John Paul Stevens on the Supreme Court, we should pause for a moment to consider the man and his legacy — if for no other reason than that this reflection informs what President Obama should look for in a successor.

Though few Americans could recognize the soft-spoken, bow-tied Justice if they met him on the street, over the past 10 years Justice Stevens has emerged from the shadows of his liberal predecessors, such as William Brennan and Thurgood Marshall, to become a towering figure on the Supreme Court and one of our nation’s greatest Justices. He has assumed a dominant role on the Court not only from his seniority, but through the force of opinion-writing and his ability — as a Republican appointee, and the Court’s only remaining WWII veteran — to bridge the Court’s ideological divide. Among his recent written opinions are numerous progressive victories for the Constitution and the rule of law, including Gonzales v. Raich (2005), Hamdan v. Rumsfeld (2006), Massachusetts v. EPA (2007), and Wyeth v. Levine (2009). It is perhaps true to say that no American since Ben Franklin has played a greater role in the course of American history after his 80th birthday than has John Paul Stevens.

Justice Stevens is irreplaceable for many reasons, not the least of which is a critical power he has held for the last 17 years as the Court’s most senior justice. This seniority has entitled him to assign the opinion-writing responsibility in any case in which he, and not the Chief Justice, was in the majority. This has meant that over the last decade, Justice Stevens has written a number of monumental opinions in which the Court’s swing Justices — Justice Sandra Day O’Connor before her retirement, and Justice Anthony Kennedy since — have sided with the Court’s liberal wing. Progressives thus need to remember that, to a certain extent, the Court is going to shift right no matter who President Obama nominates simply because the two most senior Justices will now be Antonin Scalia and Anthony Kennedy, and these conservatives will now get to assign or write many more Supreme Court opinions, a fact that will certainly affect the sweep and content of the Court’s future rulings.

So, how does President Obama replace the irreplaceable? He can’t, but here are a few things the President, and the progressive community, should keep in mind as we begin to discuss Justice Stevens’ replacement:

First, the Court needs a consensus-builder just as much as it needs a progressive firebrand. As summarized above, much of Justice Stevens’ power came from his ability to bridge the Court’s ideological divide and forge Supreme Court majorities on critical issues from environmental protection, to the scope of federal powers, to the meaning of liberty and equality. While progressives should want a Justice who passionately articulates a vision of the law, progressives also need a Justice who can successfully “count to 5” in order to produce actual victories on the Court.

Second, President Obama needs a nominee who can complete a task begun by Sonia Sotomayor: branding the Obama judiciary. During her confirmation hearings, Justice Sotomayor powerfully asserted a straightforward “apply-law-to-the-facts” approach to judging, but she came off sounding almost indistinguishable from John Roberts and his riff on judicial umpires. President Obama’s next nominee needs to improve upon Sotomayor’s performance by articulating the differences between judicial conservatives and progressives and focusing on how the Constitution and the law itself point in a progressive direction.

In particular, the Court’s ruling in Citizens United v. FEC provides an opening for this branding exercise. The Court’s 5-4 ruling, opening the floodgates to corporate spending in elections without any persuasive justification in the Constitution and the law, has outraged Americans across the political spectrum and focused the President’s attention on the courts – something also recently reinforced by the immediate challenge by conservatives to his flagship health care bill. Indeed, every aspect of President Obama’s agenda is threatened by judicial activism from the right. President Obama should use the Citizens United ruling as the centerpiece of his case for the confirmation of his chosen replacement for Justice Stevens, who wrote a brilliant and passionate 90-page dissenting opinion explaining why Citizens United ran afoul of constitutional text and history.

Finally, Justice Stevens’ dissent in Citizens United illustrates how important it is for the progressive wing of the Court to include a Justice who can go toe to toe with Justice Antonin Scalia and the Court’s other conservatives over the text and history of the Constitution. Justice Stevens has done this over and over in many opinions of the past 35 years, and won more battles than he has lost, showing that the Constitution itself points to progressive outcomes. President Obama should seek a successor who can fill this critical role.

In sum, while President Obama cannot fully replace Justice Stevens in the role he plays on the Court today, he must find a worthy successor, who, like Justice Stevens, can convince his colleagues and explain to the nation that the Constitution is a progressive document.

Cross-posted at Huffington Post.