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As Republican presidential candidates converge on South Carolina for a nationally televised debate, Senator Bernie Sanders of Vermont will be looking to solidify his lead in New Hampshire.

Mr. Sanders will head to Hanover, N.H., where he will hold a 6 p.m. news conference to announce what his campaign is describing as “an important endorsement.”

He will then hold a town-hall-style event at Dartmouth College, where the discussion is expected to focus on his plans for tuition-free higher education, climate change and economic inequality.

The events come as Mr. Sanders and Hillary Clinton have intensified their sniping less than three weeks before the Iowa caucuses. Mr. Sanders is leading in polls in Iowa and in New Hampshire, putting pressure on Mrs. Clinton to avoid a rocky start to the presidential primary election season.

Mr. Sanders has promised to release details of how he would pay for his universal health care plan before the caucuses, and Mrs. Clinton has been warning that his proposal would mean a big tax increase on the middle class.

No word on whether Mr. Sanders will offer more specifics about paying for the plan on Thursday.