Hundreds of thousands of antiwar activists flooded Senate phone lines yesterday as part of a "Virtual March" on Washington aimed at heading off a U.S. invasion of Iraq.

Protesters called and faxed senators in an innovative action, billed as a way to influence policy "without leaving your living room." Senators enlisted extra staffers to answer calls and to tally the number of constituents registering their opinions.

The calls tied up the lines of war opponents, such as Sen. Edward M. Kennedy (D-Mass.), as well as supporters of President Bush's policies, such as Senate Majority Leader Bill Frist (R-Tenn.).

Kennedy spokeswoman Stephanie Cutter said the senator's office received about 1,800 phone calls and 4,000 e-mails. "We've resorted to using cell phones because nobody can get through," she said. An aide to Sen. Frank Lautenberg (D-N.J.) estimated his office received two or three calls a minute.

The protest also jammed the phone lines to such offices as the Senate Health, Education, Labor and Pensions Committee.

While an official count was unavailable, a Washington Post survey of several Senate offices suggested that perhaps 100,000 people had their calls answered. Tens of thousands of other protesters were unable to get through. Many thousands faxed and e-mailed lawmakers' offices.

Tom Andrews, national director of the group Win Without War, which organized the effort, said the outpouring "exceeded our expectations." He estimated that a million Americans called or faxed senators yesterday, and said that 500,000 had pledged to do so on the group's Web site.

"We wanted to make it clear to the political community in Washington there are large numbers of Americans who feel very strongly about this, and we are organized and politically active," Andrews said. "We think the Senate is in the best position to do something about this very serious mistake the United States is poised to be making."

But the massive phone drive apparently did little to change the positions of lawmakers. Chris Matthews, a spokesman for Sen. Gordon Smith (R-Ore.), said many of the calls came from out of state, and said Smith continued to back Bush's apparent decision to launch a preemptive strike against Iraq.

"Obviously he takes people's views into account," Matthews said. "He also has come to his own conclusions regarding this."

Nor did Sen. John F. Kerry (D-Mass.) reverse his support for a military strike, although he issued a statement praising the protesters. "I know what it's like to be an activist trying to get the public's attention and capture the attention of the government in Washington," said Kerry, a decorated Vietnam War veteran who later led protests against that conflict.

Staff writer Ceci Connolly contributed to this report.