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Donald Trump and Hillary Clinton remain national front-runners for their party's nominations less than three weeks before the Iowa caucus, according to a new NBC News|SurveyMonkey Weekly Election Tracking Poll released Tuesday morning.

The online poll of registered voters shows Trump with 38 percent support among Republicans, with Ted Cruz receiving 20 percent and Marco Rubio receiving 11 percent.

No other Republican garners double-digit backing. Ben Carson remains in fourth place at 9 percent; Chris Christie, Jeb Bush and Rand Paul each clock in at just three percent. Carly Fiorina, John Kasich and Mike Huckabee all received two percent support.

Trump leads among each of the major age, demographic and income groups. As in previous polls, his backing is strongest with men (40 percent), seniors (44 percent), those with a high school education or less (44 percent), and those with an income under $50,000 (41 percent.)

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Among Republicans who describe themselves as independent, 34 percent support Trump, 22 percent support Cruz and 11 percent support Rubio.

The numbers are similar to the previous week’s tracking poll, which showed Trump at 35 percent and Cruz at 18 percent.

On the Democratic side, Hillary Clinton holds a 15 point lead over Bernie Sanders among Democrats nationwide. The Democratic front-runner gets the backing of 52 percent of voters, while 37 percent support Sanders. Former Maryland governor Martin O’Malley gets two percent.

Sanders bests Clinton by a wide margin with voters under 24 years old. Sixty-eight percent of these younger Democrats say they back Sanders, while just 26 percent support Clinton.

The former secretary of state has only a small advantage over Sanders with men (46 percent to 43 percent), but she boasts a significant lead with women (56 percent to 32 percent.) She also has a huge lead over Sanders with African Americans (63 percent to 20 percent) and Hispanics (54 percent to 33 percent).

That data also closely matches the NBC News|SurveyMonkey poll’s findings from last week, when Clinton registered 53 percent support and Sanders received 36 percent.

Democrats remain slightly more certain than Republicans of their choices for their party’s primary. Fifty-one percent of Democrats said they are absolutely sure they will vote for their favored candidate, while 40 percent of Republicans said the same.

Heading into Tuesday night’s final State of the Union address for President Barack Obama, 45 percent of respondents said they approve of how Obama is handling his job, while 54 percent disapprove.

This SurveyMonkey Election Tracking data for the week of January 4, 2016 through January 10, 2016 was conducted online among a national sample of 9,746 adults aged 18 and over, including 8,655 who say they are registered to vote.

For full results and methodology for this weekly tracking poll, please click here.

Sam Petulla contributed to this report.