Former Secretary of State Hillary Clinton, Vermont Senator Bernie Sanders, and former Maryland Governor Martin O'Malley are meeting for the fourth time to debate the issues – this time in Charleston, South Carolina.

　　After paying tribute to civil rights leader Martin Luther King Jr. and saying they want to raise the minimum wage, create jobs and making sure there is equal pay for equal work, all three immediately clashed on the sensitive issue of gun control.

　　Clinton has been critical of Sanders' policy on gun control, accusing the senator of doing a "flip-flop" on the question of whether gun manufacturers can be sued.

　　Democrats Hold Last Presidential Debate Before Iowa Caucuses

　　'Disingenuous'

　　Sanders called her criticism  "disingenuous," saying he has always stood up to the gun lobby and said gun control should not be a political issue, but that a small "mom and pop" gun shop should not be sued for a legal gun sale if that weapon is used in a crime.

　　Clinton accused the senator of voting with the National Rifle Association numerous times, including supporting immunity for gun manufacturers in court.

　　But it was O'Malley who stole the spotlight, when he said he has been hearing a lot of inconsistency on gun control from birth Clinton and Sanders, and that he is the only one of the three who has not changed his gun policies.

　　Health care

　　Hours before the debate, Sanders introduced a new "Medicare for All" health care plan that he says would ensure that health care is a right for every American. He said millions of Americans are still underinsured and paying too much.

　　Clinton criticized the senator, accusing him of wanting to tear up President Barack Obama's Affordable Health Care Act and start over again. She said she wants to build on the act and improve on it.

　　Sanders blamed the health insurance and pharmaceutical lobbies for keeping the cost of health care in the United States high.

　　The latest polls have Clinton and Sanders nearly tied in Iowa and give Sanders a 14 percent lead over Clinton in New Hampshire, where the first-in-the-nation primary will be held early next month.

　　A new NBC News/Wall Street Journal poll issued before the debate puts Clinton ahead of Sanders by 25 points nationally.

　　But Sanders pointed out that Clinton at one time had a 50-point lead.

　　O'Malley has been polling about 2 percent and Sunday's debate could be his last chance to convince voters that he should be the Democratic nominee.

　　Republican Party polling

　　The NBC News/Wall Street Journal poll also found one-third of people who said they would vote in a Republican Party primary said they favored Donald Trump, followed by Texas Senator Ted Cruz at 20 percent support, Florida Senator Marco Rubio at 13 percent and retired pediatric neurosurgeon Ben Carson at 12 percent.

　　In December, Trump had led the No. 2 candidate, Cruz, by just 5 percentage points. In the new poll, his lead widened to 13 points.