The 286-130 outcome was never in doubt in the House, which had passed the measure or one like it five times in recent years. The amendment's supporters expressed optimism that a Republican gain of four seats in last November's election could produce the two-thirds approval needed in the Senate as well after four failed attempts since 1989.

But an AP survey Wednesday found 35 senators on record as opposing the amendment — one more than the number needed to defeat it if all 100 senators vote, barring a change in position.

Late Wednesday, Sen. Hillary Rodham Clinton, D-N.Y., revealed that she would vote against the measure. "I don't believe a constitutional amendment is the answer," Clinton, a possible presidential candidate in 2008, said in a statement.

Sen. Ken Salazar, D-Colo., remained undecided, a spokesman said.

The House debate fell along familiar lines over whether the amendment strengthened the Constitution or ran afoul of its free-speech protections.

Supporters said there was more public support than ever because of emotions following the 2001 terrorist attacks in New York and Washington. They said detractors are out of touch with public sentiment.

"Ask the men and women who stood on top of the Trade Center," said Rep. Randy (Duke) Cunningham, R-Calif. "Ask them and they will tell you: pass this amendment."

Critics accused the amendment's supporters of exploiting the attacks to trample the right to free speech.

"If the flag needs protection at all, it needs protection from members of Congress who value the symbol more than the freedoms that the flag represents." said Rep. Jerrold Nadler (news, bio, voting record), D-N.Y., whose district includes the site of the former World Trade Center.

Since 1789, there have been more than 11,000 attempts in Congress to amend the Constitution; only 27 amendments have won ratification. The last, in 1992, prevents Congress from passing a law giving itself a pay raise before the next election. The 26th Amendment, in 1971, extended the right to vote to citizens as young as 18.

One of the most recent amendments that received congressional approval but failed to gain ratification by states was the Equal Rights Amendment. It would have set into law equality between men and women. The period for states to ratify it expired in 1982.

The last time the Senate voted on the flag-burning amendment, the tally was 63 in favor and 37 against, four votes short of the two-thirds majority needed.

Now, with more than two dozen new members, a four-seat Republican gain in the last election and a public still stung by the terrorist attacks in 2001, activists on both sides say the Senate could be within a vote or two of passage.

But the amendment's prospects faded late Wednesday when Democratic Sens. Maria Cantwell of Washington and Mark Pryor of Arkansas revealed that they would oppose it.

Possible presidential contenders who have supported the amendment in the past include Evan Bayh, D-Ind., Majority Leader Bill Frist, R-Tenn., Chuck Hagel, R-Neb., and John McCain, R-Ariz.

Sen. Joseph Biden (news, bio, voting record), D-Del., a likely presidential candidate, has said he would oppose the amendment.

The proposed one-line amendment to the Constitution reads, "The Congress shall have power to prohibit the physical desecration of the flag of the United States." For the language to be added to the Constitution, it must be approved by two-thirds of those present in each chamber, then ratified within seven years by at least 38 state legislatures.

The amendment is designed to overturn a 5-4 Supreme Court ruling in 1989 that flag burning is a protected free-speech right. That ruling threw out a 1968 federal statute as well as flag-protection laws in 48 states. The law was a response to anti-Vietnam War protesters setting fire to American flags at demonstrations.

The Senate could consider the measure as soon as next month.