COLUMBIA: Hillary Clinton is shifting her focus to Republican front-runner Donald Trump as her party looks for the best ways to challenge the billionaire's unpredictable nature in a general election.

As Clinton enters the series of Super Tuesday contests this week after a strong win in South Carolina's primary over Vermont Sen. Bernie Sanders, Democrats are stockpiling potential ammunition about Trump, reviewing court filings, requesting information about his business dealings and conducting new polls to test lines of attack.

Among the likely options: Questioning Trump's qualifications and temperament to be president, scrutinising his business practices and bankruptcy filings, and re-airing his inflammatory statements about women and minorities who will be central to the Democrats' efforts in November.

"Is this the guy you would trust with the nuclear codes? Is this the guy you would trust with your son or daughter in the military? Is this the guy you would trust to run the economy?" asked Gov. Dan Malloy of Connecticut, a Clinton backer.

While party leaders see Clinton in a favorable position against Trump, they caution that the real estate mogul has shown a mastery of the media and an ability to stay on offense throughout the Republican primaries. And they acknowledge Trump has successfully tapped into a deep vein of economic insecurity running through the electorate.

Clinton aides and allies also worry that Trump's unorthodox constituency of working-class white voters might allow him to contest more states, particularly Midwestern states like Ohio and Wisconsin that don't reliably vote for a single political party, compared to past nominees like Mitt Romney and John McCain.

But Democrats predict a Trump nomination could have a splintering effect on the Republican party.

A new survey of 800 likely Republican voters commissioned by a Democratic firm led by Stan Greenberg, who served as President Bill Clinton's pollster, found that 20 percent of Republicans are "uncertain" whether they would back Trump or Clinton in a head-to-head match-up.

The number included one-quarter of Catholics and one-third of moderates, according to the survey by the Democracy Corps' Republican Party Project shared with The Associated Press.

The poll found Trump's share of the vote drops among Catholics and moderates when Democrats describe him as an "ego-maniac," ''disrespectful to women," untrustworthy with the nation's nuclear weapons and supporting a "big oil agenda."

Stephanie Schriock, the president of EMILY's List, which backs female Democratic candidates who support abortion rights, said Trump's derogatory comments about women during the primaries would mobilize female voters.

Clinton's campaign, meanwhile, is increasingly pointing to Trump as the likely Republican nominee. Her message underscores Democrats' interest in holding Trump below 30 percent support among Hispanics, a level few think would allow the businessman to win the White House.

While Trump spends far more time attacking his Republican rivals, he has previewed some lines he would likely use against Clinton, describing her as a liar and failed secretary of state. He has made clear he's ready to take personal shots, bringing up her husband's past infidelities and suggesting she was complicit in what Trump has described as the former president's abuse of women.