Mitt Romney, photographed in Davenport, Iowa, on Oct. 29, 2012. (Emmanuel Dunand/AFP/Getty)

This post has been updated.

Mitt Romney, the Republican Party's 2012 presidential nominee, strongly condemned the flying of the Confederate flag on the grounds of the South Carolina state capitol on Saturday, prompting current GOP candidates to weigh in on a subject controversial across the "First in the South" primary state.

Romney's comments repeating his longtime position came in the wake of a shooting that left nine people dead Wednesday night at a historic black church in Charleston, S.C. Authorities were working on Saturday to determine whether the man accused of killing the nine African Americans attending a church Bible study was the author of a racist manifesto targeting blacks, Jews and Hispanics that was found on a Web site as part of an ongoing investigation.

In the wake of the shootings, critics have denounced South Carolina leaders for failing to lower to half staff a Confederate flag flying on State Capitol grounds -- and for its placement near the Capitol at all. The flag has flown atop or next to the Capitol in Columbia, S.C., since 1962. It was removed from atop the Capitol dome in 2000 and now flies at a Civil War memorial next to the Capitol.

On Saturday, Romney took to Twitter to call the flag "a symbol of racial hatred" and said it should be removed as a tribute to the victims of the shooting.

Romney first weighed in on the flag as a Republican presidential candidate in 2007, when he said "That's not a flag I recognize."

"That flag, frankly, is divisive, and it shouldn't be shown," he said during a debate sponsored by CNN.

The comments sparked outrage among some South Carolina conservatives, a key voting bloc in the Palmetto State. In protest, a group called the Americans for the Preservation of American Culture ran several radio ads attacking Romney for not supporting the state's heritage. Ultimately, Romney placed fourth in the South Carolina primary.

But Romney restated his opposition to the flag in 2012, when he won the GOP nomination. While he took a pass on running for president yet again in 2016, Rommey remains a widely influential figure in the Republican Party. He hosted a summit for former top donors two weeks ago that was attended by several presidential candidates or their representatives.

His comments Saturday came amid the struggle by several candidates to articulate whether or not the flag should remain in place -- and whether the motives of the church shooter were racist.

Ohio Gov. John Kasich, who is expected to launch a presidential campaign soon, said in a statement Saturday that the flag issue "is up to the people of South Carolina to decide, but if I were a citizen of South Carolina I'd be for taking it down."

Former Florida governor Jeb Bush said in a statement that "My position on how to address the Confederate flag is clear. In Florida we acted, moving the flag from the state grounds to a museum where it belonged."

In 2001, Bush ordered the removal of the Confederate flag from the Florida State Capitol, where it had flown since 1978.

But Bush's statement didn't explicitly call on South Carolina to do the same: "This is obviously a very sensitive time in South Carolina and our prayers are with the families, the AME church community and the entire state. Following a period of mourning there will rightly be a discussion among leaders in the state about how South Carolina should move forward, and I'm confident they will do the right thing."

Late Friday, Bush told a Tampa Republican fundraiser that "It breaks my heart that somebody, a racist, would do the things he did" in Charleston.

In Miami, Sen. Marco Rubio (R-Fla.) said Saturday that it is up to the people of South Carolina, not "outsiders," to decide whether to remove the Confederate flag.

"This is an issue that they should debate and work through and not have a bunch of outsiders going in and telling them what to do," he told reporters.

In his most expansive remarks on the deadly mass shooting, Rubio said the white man charged with the killings "carried out an act motivated by racial hatred."

"It's an atrocity. It's a horrifying instance," he added.

Rubio said he now supports Bush's decision to remove the Confederate flag from the Florida capitol and place it in a museum. But as a state legislator, Rubio co-sponsored a war monuments preservation bill that would have preserved the Confederate flag's placement on Capitol grounds.

Sen. Ted Cruz (R-Tex.), in an interview with The Washington Post, said Saturday that decisions about the flag are for South Carolina to decide, but that he understands "both sides" of the debate.

“Both those who see a history of racial oppression and a history of slavery, which is the original sin of our nation, and we fought a bloody civil war to expunge that sin," he said while campaigning in Iowa.

But, he added: "I also understand those who want to remember the sacrifices of their ancestors and the traditions of their states, not the racial oppression, but the historical traditions and I think often this issue is used as a wedge to try to divide people."

In Philadelphia, Wisconsin Gov. Scott Walker, who is poised to launch a GOP presidential campaign, began a speech on Saturday by asking for a moment of silence in memory "of those nine lives" killed in Charleston. As he watched media coverage from South Carolina, he said he was struck by how many "family and friends were already talking about forgiveness."

Later in a statement, Walker said that "The horrific crime committed on Wednesday in Charleston was done by a racist and evil man. I condemn both his acts and his beliefs."

He added later that "The placement of a Confederate flag on the Capitol grounds is a state issue and I fully expect the leaders of South Carolina to debate this but the conversation should wait until after the families have had a chance to bury and mourn their loved ones."

Carly Fiorina, the former corporate executive also running for president, didn't mention the shooting during a 20-minute speech Saturday at a Faith and Freedom Coalition conference in Washington. Asked about Romney's comments after her speech, she told reporters "personally I agree with him but I believe it's up to the people of South Carolina."

A spokesman for Sen. Rand Paul (R-Ky.) said he had no comment.

On Friday, former Texas governor Rick Perry referred to the shooting as an "accident" -- with campaign aides quickly saying that he meant "incident." His slip of the tongue in an interview sparked a social media backlash and immediately invited comparisons to his so-called "oops" moment during a 2011 debate, when he couldn't remember the three federal agencies he wanted to eliminate as president.

Perry said during the interview with Newsmax that he would be open to taking down the flag in South Carolina, saying "maybe there's a good conversation that needs to be had."

But Sen. Lindsey O. Graham (R-S.C.), who is also a GOP presidential candidate, dismissed questions about removing the flag when asked on Friday, telling CNN that "We're not going to give this a guy an excuse about a book he might have read or a movie he watched or a song he listened to or a symbol out anywhere. It's him ... not the flag."

The senator said in a statement Saturday that "There can be no doubt" that the shooting was racially motivated.

"At an appropriate time, we will move forward to have a discussion on a variety of fronts about what will make us stronger as a nation and what solutions need to be found to achieve that goal. But now, please join me in continuing to pray for the victims, for the citizens of Charleston, of my home state, and of our nation."

Jenna Johnson in Philadelphia; Sean Sullivan in Miami; Vanessa Williams in Washington; Katie Zezima in Johnston, Iowa; and Patrick Svitek of the Texas Tribune contributed to this report.