The Senate began debate Monday on a proposed constitutional amendment that would prohibit the desecration of the American flag, the latest in a series of election-year votes pushed by the chamber's Republican leaders.
Observers give the flag amendment a better chance of passing than the one to ban same-sex marriages that was defeated earlier this month.
That was another vote aimed at mobilizing the GOP's conservative base before November's midterm elections.
A vote is expected this week, before the Fourth of July congressional recess.
Sen. Arlen Specter, chairman of the Senate Judiciary Committee, compared the measure to Supreme Court decisions banning so-called "fighting words," slander, libel, obscenity and pornography involving children. As such, he said, it has no "social value."
"Flag burning is a form of expression that is spiteful or vengeful," the five-term Pennsylvania Republican said during the debate. "It is designed to hurt. It is not designed to persuade."
Sen. Patrick Leahy, the ranking Democrat on the Judiciary Committee, argued that burning the American flag was precisely the kind of speech the First Amendment is meant to protect.
"The First Amendment never needs defending when it comes to popular speech," the six-term Vermont senator said. "It's when it comes to unpopular speech that it needs defending."
He called the efforts to pass the amendment "electioneering rallying cries" that struck at the heart of what the Constitution and the flag represent.
"I would hope that all of us in this chamber champion liberty ... but when I hear some talk about cutting back on our First Amendment rights, you can see why people would wonder," Leahy said.
Democrats are not the only ones against the amendment. It also does not have the support of the Senate's No 2. Republican, Mitch McConnell of Kentucky.
"I think the First Amendment has served us well for over 200 years. I don't think it needs to be altered," McConnell said Sunday on ABC's "This Week."
The proposed amendment would roll back a 1989 Supreme Court decision that struck down state flag-desecration laws. (Watch why the debate is a fiery one -- 2:29)
The 5-4 ruling found that burning the flag was a political statement and laws barring it were an unconstitutional restriction of free speech.
The amendment, which has been rejected before, would become the 28th to the Constitution. It reads: "The Congress shall have power to prohibit the physical desecration of the flag of the United States."
The measure has the support of 56 percent of those surveyed in a CNN poll earlier this month, while 40 percent of the respondents opposed it. The poll surveyed 1,031 adults and has a sampling error of 3 percentage points.
The Senate Judiciary Committee approved the proposal on an 11-7 vote June 15. All 10 of the committee's Republicans and one Democrat -- Sen. Dianne Feinstein of California -- supported the measure.
As set forth by the Constitution, a two-thirds vote of those present in each chamber of Congress is required for an amendment to be sent to the states for ratification. It must then be ratified by at least three-fourths, or 38, of the 50 state legislatures.
The House of Representatives passed the proposed amendment last year 286-130. It needs 67 votes to pass the Senate, if all 100 senators are present.