His supporters may feel the Bern, but it’s their candidate who’s starting to sweat.

Vermont Sen. Bernie Sanders’ once-commanding lead in New Hampshire is shrinking, according to a poll released Saturday, as former South Bend, Indiana, Mayor Pete Buttigieg makes rapid gains.

Sanders has the backing of 28 percent of Democrats in the CNN New Hampshire Poll three days ahead of the state’s Tuesday primary — and Buttigieg, at 21 percent, is right behind.

The 38-year-old winner of last week’s contested Iowa caucuses has gained 6 percentage points in the last two weeks, the CNN survey found — most of it at the expense of Vice President Joe Biden, whose support faded to 11 percent.

Sen. Elizabeth Warren (D-Massachusetts) also saw a loss in the poll, dropping down to single digits — 9 percent — for the first time. Amy Klobuchar was unchanged at 5 percent. Mayor Mike Bloomberg, who is not running in Tuesday’s contest, came in with 2 percent support in the Granite State.

The CNN survey, which was done before Friday’s debate, has a 5.1 percent margin of error.