Hillary Rodham Clinton has caught up to Bernie Sanders in the key early-voting state of New Hampshire, a poll released Wednesday shows.

The WBUR survey giving Clinton a four-point lead is the latest to record an upswing for Clinton following last week’s Democratic debate. Her New Hampshire lead is within the poll’s margin of error, meaning she is likely roughly tied with Sanders, or slightly ahead. The reversal suggests Clinton has made up ground lost over a summer of bad news about her private e-mail system, and Democratic disaffection that benefited Sanders.

The poll showed Clinton capturing 38 percent of support among New Hampshire Democrats surveyed to 34 percent for Sanders, an independent senator from next-door Vermont. The same poll had Sanders in the lead at 35 percent to 31 percent in September. A Suffolk University/Boston Globe survey late last week put Clinton at 37 percent and Sanders at 35 -- essentially a tie but the first time in many weeks that major surveys had put Clinton ahead.

The gains for Clinton are notable because New Hampshire represented the worst of Clinton’s summer slide. Although she is spending more time and money in New Hampshire and Iowa than anywhere else, her support in both states had fallen. New Hampshire was the only state in which Sanders, a surprise success story this summer, had moved ahead of the longtime Democratic front-runner.

Clinton’s New Hampshire turnaround is not large and not a sure thing. A Bloomberg/St. Anselm College poll over the weekend showed Sanders ahead in the state 41 percent to Clinton’s 36.

Still, the latest New Hampshire results are in line with national surveys that show a rebound for Clinton in October, and especially since the debate.

Aided by her performance in the Oct. 13 debate, Clinton has regained much of the ground she lost nationally and holds a dominating lead over Sanders, a Washington Post-ABC News poll suggested Tuesday. Clinton is the first choice of 54 percent of registered Democrats and Democratic-leaning independents. That compares with 42 percent in September, by far her lowest level of support over the past two years, and 63 percent in July. Sanders runs second at 23 percent, almost identical to his September number. It is the first time his support has not changed from one month to the next.

Vice President Biden, who has yet to announce whether he will join the Democratic race, runs third amid signs of slippage over the past month. If he were to decide not to run, the Post poll indicates that much of his current support would go to Clinton rather than Sanders.

Clinton has another opportunity this week to solidify her gains, and perhaps begin to reverse the trend of voters saying they do not find her trustworthy. She will testify Thursday before the House committee investigating the Benghazi attacks, a venue her supporters think will allow her to showcase positive elements of her tenure as secretary of state. Clinton has called the Republican-led committee a partisan tool used to damage her standing in the 2016 presidential race.

Clinton has said she will answer questions but doubts she has much new to offer about the attacks that killed four Americans, including the sitting U.S. ambassador to Libya. Clinton was secretary of state at the time. In her 2014 memoir "Hard Choices," Clinton called the deaths her lowest moment in the job. Previous investigations have found no evidence she played a direct role in any decision that might have averted the tragedy.

Scott Clement contributed to this report