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Is Donald Trump losing steam in early states?

In a new poll of early contest states released Sunday, Donald Trump continues to dominate the GOP field -- but the numbers show his closest competitors are gaining ground.

Among Republican primary voters in the NBC News/Wall Street Journal/Marist poll, the real estate magnate holds a five-point lead over Carly Fiorina in New Hampshire, the nation's first primary state. Trump comes in at 21 percent, with the former tech executive not far behind at 16 percent.

Former Florida Gov. Jeb Bush came in third with 11 percent of the vote, while Florida Sen. Marco Rubio and retired neurosurgeon Ben Carson tied for fourth place with 10 percent.

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It's a sharp contrast from last month's poll, which showed Trump trouncing his nearest rival, Ohio Gov. John Kasich, by 16 points. Trump garnered 28 percent of the vote to Kasich's 12 percent.

In Iowa, Carson is playing catch-up to Trump, coming in second among possible GOP caucusers. The soft-spoken doctor trails Trump by five points, 19 to 24 percent. Fiorina comes in third with 8 percent. Bush follows at 7 percent, with Rubio, Texas Sen. Ted Cruz and Louisiana Gov. Bobby Jindal each at 6 percent.

The Democratic field remained largely unchanged from last month in the two early states -- though Vice President Joe Biden could even out the playing field if he joined the race.

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In Iowa, Hillary Clinton still leads at 47 percent, with Vermont Sen. Bernie Sanders getting 36 percent of possible caucus-goer support. Previously, Clinton led Sanders with the same 11-point margin, 48 to 37 percent. In this month's poll, former Maryland Gov. Martin O'Malley registers in the single digits with only 4 percent.

With Biden added to the mix, however, Clinton's lead lessens: The former secretary of state would poll at 33 percent, with Sanders at 28 percent and Biden at 22 percent.

In New Hampshire, Sanders remains on top at 48 percent, with Clinton behind by 9 points -- nearly the same as last month's numbers. If Biden jumps into the White House contest, a likely scenario considering his recent talks with political advisers and donors, Clinton falls further behind. Sanders would have 42 percent of the votes, with Clinton at 28 percent and Biden at 18 percent.

The surveys were conducted from September 23-30, after the second Republican debate in Simi Valley, California.