PHILADELPHIA (CBS) – Former Vice President Joe Biden remains out front in the latest Democratic primary poll, but his lead is narrowing somewhat as his numbers have gone flat. Biden holds an 11-point advantage over his next closest rival, Vermont Sen. Bernie Sanders, according to a Quinnipiac University National Poll released Tuesday.

Biden leads Democrats and voters leaning Democratic with 30% – down from 38% in April – but Sanders, Massachusetts Sen. Elizabeth Warren and South Bend Mayor Pete Buttigieg are picking up steam in the latest poll.

Sanders finished second in the latest poll with 19% – up 3% from Quinnipiac’s May 21 poll.

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Warren was third at 15%, a two-point increase from last month’s poll. Buttigieg came in fourth at 8%, up from 5% in last month’s poll.

California Sen. Kamala Harris was fifth with 7% and former Texas Rep. Beto O’Rourke was sixth at 6%.

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No other Democrat running had more than 1% with 15 candidates not even cracking 1%. There are 24 total candidates running for the Democratic nomination.

In the 2020 race for president, Biden also remains ahead of President Donald Trump by 13 points – 53% to 40%.

Sanders has a nine-point lead over Trump (51% to 42%), Harris has an eight-point lead over Trump (49% to 41%), Warren has a seven-point lead Trump (49% to 42%) and Buttigieg has a five-point lead over Trump (47% to 42%).