Most political observers assumed that if Hillary Clinton were to hit a stumbling block in the Democratic primaries, it would be in Iowa, where she placed third in 2008. But two new polls this week show her lead in New Hampshire shrinking rapidly as Vermont Sen. Bernie Sanders gains ground.

Suffolk University poll released Tuesday morning found Clinton leading Sanders by 10 points, 41 percent to 31 percent, among likely voters. (They're followed by Vice President Joe Biden at 7 percent, Maryland Gov. Martin O'Malley at 3 percent, and both former Rhode Island Gov. Lincoln Chafee and former Sen. Jim Webb of Virginia at 1 percent.)

The Suffolk numbers come on the heels of a poll from the Morning Consult out Monday: That poll put Clinton at 44 percent and Sanders at 32 percent, with no other candidate reaching double digits.

It's a surge for a candidate who, when he entered the race, was trailing Clinton in New Hampshire polls by more than 30 points. A WMUR/UNH poll conducted following Sanders's campaign launch in late April put him at 13 percent and was well below Clinton's 51 percent. Another, from Bloomberg and St. Anselm College in early May, had Sanders at 18 percent and Clinton at 62 percent.

For now, however, the trend seems limited to New Hampshire: Clinton's lead in Iowa remains considerably larger. Morning Consult's numbers there have her leading all possible challengers by more than 40 points, as did recent polls from The Des Moines Register and Quinnipiac.

The Suffolk poll surveyed 500 likely voters from June 11 to 15 and has a margin of error of plus-or-minus 4.4 percentage points; the Morning Consult poll surveyed 279 likely Democratic primary voters—through a mix of live-caller phone polling and online surveys—from May 31 to June 8 and has a margin of error of plus-or-minus 6 percentage points.

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