Different political groups are vying for influence on the future of the U.S. Supreme Court. (J. Scott Applewhite/AP)

The debate over a replacement for the late Justice Antonin Scalia marks the beginning of a ferocious battle for ideological control of the U.S. Supreme Court that could drag on for years and see the court swing multiple times between the political poles.

Groups on both sides of the political divide are raising money and marshaling political ammunition for a protracted fight over what kind of legal thinkers should sit on the nation’s highest court. Civil rights groups, labor unions and environmentalists are preparing for a faceoff with a conservative coalition of social activists and business interests. Forces on both sides are conducting polls and focus groups and are mobilizing their members with online appeals. Conservatives are also researching the records of potential Obama nominees and preparing to launch attack ads as soon as the president makes a selection.

The Scalia vacancy technically gives Obama the chance to establish a liberal majority on the court for the first time in decades, but even if he manages to seat a new justice in the face of blanket GOP opposition, the victory could be fleeting.

Carrie Severino, chief counsel and policy director of the conservative Judicial Crisis Network, describes the fight over the court vacancy as “the opening act” in a broader struggle to prevent liberals from reasserting their influence over the nation’s legal system.

Four cases that could re-shape the country will be heard when the Supreme Court meets this term without Justice Antonin Scalia. Scalia consistently expressed conservative views when reviewing court cases. (Claritza Jimenez/The Washington Post)

“Their sole goal is to cement liberal dominance over the Supreme Court. It’s incredibly high stakes,” said Severino, who clerked for Justice Clarence Thomas and whose group has already launched two separate, costly ad campaigns urging key Republicans and Democrats not to consider an Obama nominee to replace Scalia.

“We’ve been looking at the Supreme Court for some time, knowing these vacancies can come up,” she said, adding that her group has already spent more than $1 million in ads and has plenty in reserve to spend on an extended campaign.

Scalia’s death at age 79 shows the peril of making predictions about the court’s future, but the age range among the current justices would suggest that a Republican successor to Obama could have a greater impact on remaking the court than a Democrat, especially if Scalia’s seat stays vacant into the next administration. Simply put, the court’s liberal bloc is older and may offer more opportunities for replacement.

When the new president is inaugurated, Justice Ruth Bader Ginsburg will be almost 84. Anthony M. Kennedy will be 80, and Stephen G. Breyer will be 78. Replacing Ginsburg and Breyer, both appointees of President Bill Clinton, with conservatives would instantly shift the court’s balance for years, even if an Obama appointee were to replace Scalia. (The next oldest justice is Thomas, who was nominated by George H.W. Bush and will be 68 this summer.)

Ginsburg, Kennedy and Breyer will try to stagger their departures if possible; the justices know that the Senate would have trouble dealing with even one vacancy at a time. But their ages are one reason that presidential candidates of both parties are pointing to the court as one of the biggest opportunities for the next president.

Conservatives have longed to replace Kennedy, who was appointed by Ronald Reagan but has sided with the court’s more liberal members on several occasions.

As the fight begins, there is no question that Republicans have a more robust political machine in place for a sustained fight. More than three decades ago, wealthy conservatives established the Federalist Society, aimed at bringing the nation’s legal system more in line with their values. The Judicial Crisis Network started in 2005 and has worked on both federal and state judicial races: It has booked more than $604,000 in television ads this month in a single Arkansas Supreme Court race, according to the Brennan Center for Justice, more than both candidates’ campaigns combined. Several other influential conservative groups, including Americans United for Life and the National Rifle Association, are poised to join the fight.

But liberals and other left-leaning groups may have even more at stake. In recent years, the GOP has expanded its control over state legislatures and governorships, even as Republicans were taking over the majorities in the House and Senate. As a result, Democrats and their liberal and progressive allies are more reliant on court decisions to overturn laws and policies that conservatives adopted at both the state and federal levels.

This year, the Supreme Court is poised to rule on several of those pivotal cases, including unions’ ability to collect mandatory dues from public employees and new state requirements on how abortion clinics operate.

This has energized a broad array of progressive groups, many of whom began working on judiciary and Senate reforms four years ago through a new coalition called the Democracy Initiative.

“We’ll organize on this in ways that are similar to the ways we’ve mobilized to protect public lands, and clean air and clean water,” said Sierra Club Executive Director Michael Brune, whose group has 2.1 million members and helped start the Democracy Initiative.

Brune and others are already calling donors to ask for a fresh influx of funds to amplify their message in this year’s presidential and congressional campaigns. On Tuesday, he will join in a conference call with NAACP President Cornell William Brooks and former labor secretary Robert Reich to mobilize activists to gather in Washington in mid-April for a “Democracy Awakening” rally that will make the future of the Supreme Court a central issue.

Should they succeed in helping to seat an Obama nominee this year, political scientists have identified several issues that could play out differently with a liberal majority. Campaign finance laws would be a fertile area for change. The court’s liberals are far more sympathetic to legislative attempts to curb the role of money in politics, and both Democratic presidential hopefuls, Hillary Clinton and Bernie Sanders, have declared that overturning the court’s 5-to-4 Citizens United decision would be a priority in how they chose court nominees.

Additional restrictions on the death penalty would be likely with a liberal majority, and elimination of capital punishment would not be out of the question. Voting-law restrictions such as voter-identification laws would face a far more hostile court. Abortion rights activists would be far more likely to try to bring to the high court the wave of state restrictions on abortion in an attempt to overturn those laws.

But if a Republican president fills Scalia’s seat, names Ginsburg’s eventual replacement and shores up the conservative wing of the court by naming Kennedy’s successor, the picture would be just the opposite.

Nan Aron, president of the Alliance for Justice, said Scalia’s death “was a wake-up call for progressives” because it “crystallized the stakes.” But, she said, the larger issue is whether those on her side are ready to engage in a crusade that will last long after Obama leaves office.

“The question is whether people, particularly the base of the Democratic Party, are not just engaged in filling this vacancy, but in all vacancies that come up in the future,” she said.