WASHINGTON — Thrusting the issue of eminent domain into the presidential campaign spotlight, Senator McCain is vowing to counteract a 2005 Supreme Court decision that enhanced the government’s ability to seize private property, and he says he may seek a constitutional amendment to overturn it.

In a speech yesterday in Iowa, the Arizona senator called the Kelo v. City of New London decision “one of the most alarming reductions of freedom in our lifetimes.”

The Supreme Court, in a 5–4 ruling in 2005, upheld a Connecticut city’s right to take private property for the “public purpose” of promoting economic development. The decision sparked a nationwide debate on the appropriate exercise of eminent domain and prompted a myriad of legislative efforts to curb its use by states and municipalities.

Characterizing the ruling as a threat both to property rights and the free market, Mr. McCain pledged to appoint “strict constructionist” judges “who respect the Constitution and understand the security of private property it provides.”

But he did not stop there, adding that if necessary, he would “seek to amend the Constitution to protect private property rights in America.”

Until yesterday, the eminent domain issue had not figured prominently in the White House race, but Mr. McCain’s speech could force his chief rivals for the Republican nomination, Mayor Giuliani and Mitt Romney, to confront the issue. A spokesman for the former Massachusetts governor pointed to vetoes that Mr. Romney issued to legislation in 2005 and 2006 that recommended changes specifically to prohibit “eminent domain taking for private development purposes.” And in an appearance on the “Hugh Hewitt Show” in 2005, Mr. Romney said the Supreme Court had made “an error in judgment” in the Kelo decision.

Mr. Giuliani’s position is less clear. Asked for the former mayor’s stance on the Kelo ruling and eminent domain, a campaign spokeswoman, Maria Comella, reiterated his repeated pledges to appoint strict constructionist judges “in the vein of Roberts, Scalia, and Thomas.” Justices Scalia and Thomas dissented from the Kelo decision, while Chief Justice Roberts had not yet joined the court.

Mr. McCain’s aggressive stance on the issue comes as he is trying to rebuild his candidacy amid fund-raising woes and the exodus of many of his top advisers.

His support for a constitutional amendment on property rights surprised even the staunchest critics of eminent domain abuse, who said there had been little discussion of such an effort. “There isn’t a serious movement afoot,” a senior attorney at the libertarian Institute for Justice who argued the Kelo case before the Supreme Court, Scott Bullock, said.

Mr. Bullock said he was focused on efforts to pass federal legislation that would withhold economic development funding for state and local governments that invoke eminent domain for private development projects. The House approved the legislation overwhelmingly last year before it stalled in the Senate. Lawmakers have vowed to try again, and Mr. McCain is expected to co-sponsor a Senate version. A constitutional amendment push “would be more of a diversion,” Mr. Bullock said. “The legislation is something that is much more feasible. It would provide a lot of protection for property owners.”

Legislation cracking down on eminent domain faces opposition from lobbying groups representing developers and municipalities, including the American Planning Association and the National League of Cities. Eminent domain is a “valuable tool” for cities and is best decided on a local level, a league spokeswoman, Sherry Conway Appel, said.

Policy on eminent domain has particular resonance in New York City, where developers and community activists have battled over property rights for the Atlantic Yards project in Brooklyn and for Columbia University’s expansion in Harlem. While the state is moving ahead with plans to use eminent domain in the $4 billion Atlantic Yards development, Columbia announced last month that it would not seek to seize residential homes for its construction in Manhattanville. The university has not ruled out using eminent domain to acquire several commercial sites it is seeking.

Mr. McCain’s position puts him at odds with Mayor Bloomberg, who has championed the use of eminent domain to revitalize blighted areas of the city, frequently citing the transformation of Times Square as an example. The mayor last year lobbied lawmakers both in Albany and Washington against legislation that would restrict its use.

Mr. McCain yesterday won praise, however, from one of Mr. Giuliani’s fiercest critics, Norman Siegel. The former head of the New York Civil Liberties Union is representing Harlem residents opposed to Columbia’s expansion. “Congratulations to John McCain,” Mr. Siegel said. “It definitely should be a presidential issue.”

Eminent domain was not a divisive issue during Mr. Giuliani’s tenure at City Hall and didn’t emerge “on the radar screen” until shortly before he left office, Mr. Siegel said.