WASHINGTON  - The next president of the United States may be able to appoint several Supreme Court justices " the powerful judges whose rulings affect the daily lives of Americans " yet the issue is underplayed on the presidential campaign trail. The US Supreme Court has nine justices, of which five are considered conservative and four are considered moderate or liberal. Supreme Court experts believe that at least three of the justices " John Paul Stevens, 88, Ruth Ginsburg, 75, and David Souter, who at 68 has always felt uncomfortable in the spotlight " are likely to retire in the next four years. While two of them were appointed by Republican presidents, all three are now strongly identified with the court's liberal bloc. If Republican John McCain is elected president he could appoint conservative judges and steer the court firmly to the right " but if Democrat Barack Obama is elected and appoints liberal judges, he could only maintain the current balance, barring unforeseen health crises among the other court members. "The composition of the high court is one of the most important issues at stake in the November election," wrote online news site Slate senior editor Dalhia Litwick in a recent editorial. "While the justices cannot bring down gas prices or bring the troops home, their decisions in the coming years will affect just about everything else," the legal expert wrote. This year many of the court's decisions were reached by consensus, such as those concerning business rights and workplace discrimination. But the conservative-liberal split was sharp on crucial issues like the legal rights of prisoners held at the US military base in Guantanamo Bay, Cuba, the ruling stating that capital punishment must be reserved for murder cases, and the overturn of the ban on handguns in the home in the nation's capital. Obama has promised, if elected, to appoint justices showing "empathy." McCain has vowed to name only conservative judges like Chief Justice John Roberts and Samuel Alito, both in their 50s and appointed in 2005 by President George W. Bush. Adding one, two or even three conservative judges would heavily tip the Supreme Court's balance to the conservative side. While McCain and Obama have commented on the Supreme Court's latest rulings, no new rulings are expected before the election, and the crucial issue is likely once again to underplayed on the campaign trail. McCain has made some overtures to the Republican party's right-wing base, saying he would appoint conservative judges, while Obama has stressed party unity and steered away from bipartisan squabbling in his campaign. Under the US constitution all Supreme Court nominations must be confirmed by the Senate, where Democrats will likely increase their majority in the November election regardless of the presidential vote outcome. So if McCain is elected president, there would likely be an epic confirmation battle over his future choice for a Supreme Court justice. In the current court the swing vote is held by Justice Anthony Kennedy " nominally a conservative but who voted to for Guantanamo prisoner rights and against imposing the death penalty on child rapists. Conservative activists have seized on these two 'setbacks' to stress the court's need for more 'good judges,' in order to deprive Kennedy of this pivotal role. Liberals, on the other hand, have raised the alarm. "One more Bush Justice on the Court, and the decision would likely have gone the other way," said Kathryn Kolbert, president of the left-wing group People for the American Way. Kolbert's comment came after the Guantanamo ruling giving war-on-terror prisoners the right to challenge their detention in a civilian court. "That's why it's so important for Americans to realize that in this election year, the Supreme Court is on the ballot," she said.