The narrow defeat of a proposal to ban flag desecration marks the second time in a month Senate Republicans have lost bids to amend the Constitution in ways designed to inspire social conservatives to vote in the midterm elections.
The 66-34 tally on the flag amendment Tuesday was one less than the two-thirds, or 67 votes, required to send it to the states for ratification. The House cleared the two-thirds threshold last year, 286-130.
Sponsored by Sen. Orrin Hatch, R-Utah, the amendment read: "The Congress shall have power to prohibit the physical desecration of the flag of the United States."
A proposed amendment earlier this month to ban gay marriage suffered a more decisive defeat, killed on a test vote.
Winning isn't the only goal for those measures or other social policy proposals congressional Republicans will bring up this year in an effort to energize their base of voters.
House Republicans intend to hold votes this summer and fall touching on abortion, guns, religion and other priority issues for social conservatives, part of an attempt to improve the party's prospects in the midterm elections.
The "American Values Agenda" also includes the gay marriage amendment, a prohibition on human cloning and possibly votes on several popular tax cuts.
The flag amendment's cliffhanger defeat a week before Independence Day represented Congress' response to Supreme Court rulings in 1989 and 1990 that burning and other desecration of the flag are protected as free speech by the First Amendment to the Constitution.
Senate supporters said the flag amounts to a national monument in cloth that represents freedom and the sacrifice of American troops.
"Countless men and women have died defending that flag," said Majority Leader Bill Frist, R-Tenn., closing two days of debate. "It is but a small humble act for us to defend it."