NEW HAMPSHIRE — Democratic presidential contenders Hillary Clinton and Bernie Sanders take an increasingly combative tone into their first one-on-one debate on Thursday, cranking up a fight over who is best suited to lead the party’s liberal agenda on the economy and healthcare.

Five days before New Hampshire voters render a judgment in the second of the state-by-state presidential nominating contests, Clinton and Sanders will square off on MSNBC at 9 p.m. EST (0200 Friday GMT) in Durham, New Hampshire.

Polls show Sanders, a U.S. senator from neighboring Vermont, has a comfortable lead over Clinton in New Hampshire after surprising the front-runner by managing a virtual tie with her in the kickoff contest in Iowa on Monday.

In the two days since, the Democrats have clashed sharply over who is more capable of carrying out the party’s liberal proposals to battle income inequality, bolster healthcare coverage and rein in Wall Street.

The exchanges intensified ahead of the debate, which will be the first since former Maryland Governor Martin O’Malley dropped out on Monday night. It also is one of four debates Clinton and Sanders agreed to add to the schedule.

Sanders, a democratic socialist who has galvanized the party’s liberal wing, accused Clinton on Wednesday of being a progressive on some days and a moderate on others. He cited her shifts on trade and energy policies and her 2003 Senate vote to back the Iraq war, which she has called a mistake.

Clinton said she was amused to see Sanders setting himself up as the “gatekeeper” for who was a progressive and that President Barack Obama would not qualify under his definitions.

“I know where I stand, I know who stands with me, I know what I’ve done,” Clinton, a former secretary of state and U.S. senator, said at a town hall on Wednesday night where she and Sanders spoke separately.

Clinton has tried to play down expectations for her performance in New Hampshire, where she came from behind for an upset victory in the 2008 campaign just days after losing badly to Obama in Iowa.

The surprisingly strong performance by Sanders in Iowa is likely to prolong a race that Clinton entered as the prohibitive favorite.

In addition to previously scheduled debates in Wisconsin and Florida, the candidates added one in March in Flint, Michigan, to draw attention to the city’s contaminated water crisis ahead of the Michigan primary. They also will debate in April and May.