The battle over Supreme Court nominee Samuel A. Alito Jr. moved to the nation's airwaves yesterday, as conservative and liberal groups bought advertising time that could dwarf the meager efforts made in this year's other two confirmation efforts.

As Alito continued his round of courtesy calls on senators, his critics launched new television ads painting him as a tool of right-wing conservatives. Supporters, meanwhile, announced ads that say his opponents, not Alito, are outside the political mainstream.

The ad buys, as well as the early clashes between the interest groups, are another signal that Alito's confirmation will be more contentious and hard-fought than was that of Chief Justice John G. Roberts Jr., who was confirmed in September to replace the late William H. Rehnquist.

In part, that is because Rehnquist was a conservative whose replacement by Roberts did not significantly shift the court's balance. But Alito is tapped to succeed retiring Justice Sandra Day O'Connor, a swing voter who has cast pivotal votes on a host of issues including affirmative action and abortion.

With Roberts, most liberal interest groups held their fire, waiting to announce their opposition until just before the Senate Judiciary Committee convened his confirmation hearing. This time, they are moving much faster.

The nation's largest civil rights coalition, the Leadership Conference on Civil Rights, announced its opposition to Alito yesterday, criticizing his record on affirmative action, voting rights, job discrimination and other subjects. The announcement followed earlier ones by the liberal groups NARAL Pro-Choice America and People for the American Way.

In what it called a "substantial buy," a liberal coalition of those groups -- IndependentCourt.org -- launched a TV ad that will run nationally on Fox News and CNN, and on ABC, NBC and CBS affiliates in Maine and Rhode Island, which are home to three moderate Republican senators. The ad pictures conservative commentators Pat Buchanan and Rush Limbaugh and highlights a memo Alito wrote during the Reagan administration in which he said "the Constitution does not protect a right to an abortion."

Alluding to conservatives' successful battle to defeat President Bush's previous nominee to fill O'Connor's seat, White House counsel Harriet Miers, an announcer intones: "The right wing has taken over the West Wing. Don't let them take over your Supreme Court."

Conservative groups, meanwhile, are targeting Democratic senators in states won by Bush in 2004. The conservative Committee for Justice announced a modest radio and television ad campaign that will air next week in Nebraska, West Virginia, North Dakota, South Dakota, Colorado, Arkansas and Montana.

The ad notes that in 1990 the Senate unanimously confirmed Alito to his current post as an appeals court judge. It devotes most of its attention, negatively, to liberal groups such as People for the American Way.

"Their agenda is clear," the announcer says. "They want to take God out of the Pledge of Allegiance and are fighting to redefine traditional marriage. They support partial-birth abortion, sanction the burning of the American flag . . ."

Committee for Justice Executive Director Sean Rushton said the group, which did not run ads for Roberts, will spend less than $250,000 on the campaign. "The left has signaled that this is going to be a tougher debate," he said. "A full-court press from the left allows us to stand up and enunciate our views, and we believe that's a debate that's very winnable."

Some political analysts questioned the effectiveness of the ads.

"Nobody's paying attention to this," said Charles Cook, editor of the independent Cook Political Report. "What you see is activists on each side posturing, but the American people aren't engaged in this debate. To the extent they know anything about Judge Alito, he seems fine." People are more interested in "the war in Iraq, budget problems and the fact that the wheels are coming off the bus on Capitol Hill," Cook said. "As far as the American people are concerned, there's not a Supreme Court nomination fight."

Nonetheless, groups on the left and right responded quickly to the ads. Conservatives accused liberals of distorting Alito's record, and liberals accused conservatives of using misleading attacks to "change the subject" from a discussion of Alito's legal and political philosophy.

Brad Luna, director of the Human Rights Campaign, a gay-rights group, condemned the ad attacking People for the American Way, calling it "a reprehensible scare tactic usually saved for gutter-style political campaigns, not for a Supreme Court nomination."

Wendy E. Long, counsel to the Judicial Confirmation Network, said it is no surprise that "extremist liberal groups" are trying to "strong-arm the whole Democratic Party and the Senate from doing its job and giving Judge Alito a fair up-or-down vote for the Supreme Court."

Staff writer Charles Babington contributed to this report.

Supreme Court nominee Samuel A. Alito Jr. arrives for a visit with Sen. Joseph R. Biden Jr. (D-Del.) on Capitol Hill.