US Sen. Bernie Sanders (I-Vermont) continues to rise in the polls.

A new CNN/ORC poll released Monday showed Sanders with the biggest leap among any candidate in the 2016 field. And a new poll in the first-in-the-nation primary state of New Hampshire found him slightly expanding his lead there over former US Secretary of State Hillary Clinton.

In Monday's CNN poll, Sanders garnered 29% support nationally, up 5% from a similar CNN poll released a month ago.

That still put him far behind Clinton, who grabbed 45% of national Democratic primary voters. Clinton, the Democratic presidential front-runner, has seen support rebound among Democratic voters since bottoming out at 37% in a similar CNN poll released in early September. She moved up to 42% in mid-September, meaning she rose three points in Monday's poll.

And in New Hampshire, a new Franklin Pierce University/Boston Herald poll found Sanders with an eight-point lead over Clinton in the state. That was up a point from the last FPU/Boston Herald poll, and his lead increases to 10 points without Vice President Joe Biden in the survey.

Sanders' and Clinton's rises come as several other lower-tier competitors appear to have sunk even further in the polls. In the CNN survey, Biden, who is still mulling an entry into the race, has dipped four points since a mid-September CNN poll showed him with 22% support among Democratic voters. Former Maryland Gov. Martin O'Malley's support in Monday's poll has sunk below 1%.

It's not clear whether Sanders' surge is a result of his performance at the first Democratic debate. According to CNN, almost 60% of Democratic voters surveyed said Clinton did the "best job" in the debate, compared to 35% who said Sanders prevailed.

But Sanders had the largest social-media moment of the night with his dismissal of the legitimacy of Clinton's email controversy.

For her part, Clinton's summer downslide in polls appears to be leveling off. In the first major poll released following last week's debate, a Suffolk University/Boston Globe poll of New Hampshire Democrats found Clinton taking a slight lead in the Granite State for the first time in several months. In that poll, 37% of Democratic voters said they'd support Clinton, compared with 35% who'd support Sanders.