(Recasts throughout with debate, amendments)
By Harriet McLeod
CHARLESTON, S.C., July 8 (Reuters) - The campaign to remove the Confederate battle flag from South Carolina's capitol grounds marched forward on Wednesday, as the House of Representatives emotionally debated the banner symbolizing slavery and racism for many and Southern heritage for others.
As debate on a proposed law to take down the flag began in the House of Representatives, the South Carolina Law Enforcement Division said it was investigating threats sent to legislators on both sides of the issue.
The state Senate first took up the bill on Monday less than three weeks after nine black worshippers were gunned down on June 17 during Bible study at a historically black church in Charleston. A white man, Dylann Roof, is accused in the massacre.
The battle over the banner nicknamed the "Stars and Bars" was stoked by photos of Roof showing the 21-year-old man posing with a Confederate flag on a website bearing a racist manifesto.
The murders sparked a bipartisan wave of repudiation across the South, from politicians to businesses, led by South Carolina's Republican Governor Nikki Haley.
On Tuesday, the Republican-controlled Senate approved the bill by an overwhelming 36-3. The legislation - required before the flag can be moved to a museum - went to the House.
If the lower chamber passes it, the bill will go to the governor to be signed into law, perhaps as soon as Thursday.
Wednesday's House debate was civil as conservative defenders of the flag introduced dozens of unsuccessful amendments seeking to replace it with various alternatives, such as a cast bronze replica that would be affixed to the Confederate Soldier Monument on the State House grounds. The flag now flies on a pole next to the monument.
Another amendment sought to put the issue to a statewide referendum.
Representative Wendell Gilliard, a black Democrat from Charleston, urged support for the bill as a tribute to the slain church members' families and their expression of forgiveness for the accused killer.
"This has brought forth a new understanding and new ways of seeing ways to peace and justice. ... The right thing to do is the gentle laying down of the past and a hopeful road to the future," Gilliard said.
The flag's dwindling defenders deny its association with slavery, saying it honors those who fought and died for the state and the southern Confederacy on the losing side of the 1861-1865 Civil War.
House members who support the flag looked to history - and prayer - for answers.
"I grew up holding that flag in reverence because of the stories of my ancestors carrying that flag into battle," Representative Michael Pitts, a white Republican, told the House.
"People gave their lives not to defend slavery but because they were called up to defend a state," added Republican Mike Ryhal, who is also white.
Another white Republican, Eric Bedingfield, said the Civil War was not over slavery but about "fighting a repressive federal government," adding that the fight goes on today.
South Carolina's flag fight is a return to a controversy that arose decades ago. The banner was originally raised atop the State House in 1961 - joining the state flag and the U.S flag - in what was described as a commemoration of the centennial of the Civil War.
Others, however, saw it as a slap in the face to the black civil rights movement then gaining momentum.
In 2000, flag opponents scored a partial victory, getting it moved from atop the capitol to its place by the monument, only yards from the State House entrance.
The current bill's swift progress marks a dramatic turnaround in sentiment from only a few months ago, largely attributed to a national wave of sympathy for the nine victims at Emanuel African Methodist Episcopal church in Charleston, about two hours drive southeast of the state capital, Columbia.
The church pastor, Reverend Clementa Pinckney, was also a widely admired state senator.
A Gallup poll released on Wednesday showed 54 percent of Americans view the Confederate flag as a symbol of Southern pride rather than a symbol of racism, down from 59 percent in 2000 and 69 percent in 1992. Another 34 percent believe the flag is a racist symbol, said Gallup.
The poll was based on telephone interviews with a random sample of 2,013 adults aged 18 and older. (Writing by David Adams; Additional reporting by Suzannah Gonzales; Editing by Cynthia Osterman, Richard Chang and Jonathan Oatis)