Clinton holds 15-point lead on Sanders nationally
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Hillary ClintonHillary Diane Rodham ClintonNo Hillary — the 'Third Way' is the wrong way The dangerous erosion of Democratic Party foundations The Hill's Morning Report - Presented by Facebook - Democrats see victory in a voting rights defeat MORE has a nearly 20 percent edge in voter support over Sen. Bernie SandersBernie SandersSunday shows preview: US reaffirms support for Ukraine amid threat of Russian invasion Filibuster becomes new litmus test for Democrats Gallego says he's been approached about challenging Sinema MORE (I-Vt.) in the 2016 Democratic presidential primary, according to an NBC News/Survey Monkey poll released early Tuesday.

Clinton remains the party’s front-runner less than a month before the first votes are cast in Iowa.

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She takes 52 percent voter support, followed by Sanders’s 37 percent. Former Gov. Martin O’Malley ranks a distant third, with 2 percent.

About 8 percent do not know which Democratic contender they will back. Another 1 percent have no answer.

Tuesday’s results show that Democrats are relatively adamant about the candidate they are supporting in their party’s primary.

About 51 percent say they are “absolutely certain,” while another 31 percent state there is a “large chance” they have their contender.

Approximately 15 percent are 50-50, pollsters discovered, while 3 percent said there is a “small chance” they are decided and 1 percent have no answer.

NBC News and Survey Monkey surveyed 2,619 registered Democratic voters from Jan. 4 to 10, with a 2.4 percent margin of error.

Clinton leads Sanders by roughly 13 percent nationwide, according to the latest RealClearPolitics average of polls. He remains competitive with a 4.3 percent lead in New Hampshire, according to an index of Granite State polls.