Poll: Trump holds 17-point lead
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Donald TrumpDonald John TrumpKoch-backed group launches six-figure ad buy against Heitkamp Anti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight MORE continues to hold a big lead in the race for the 2016 Republican presidential nomination, leading his closest rivals by double digits in an NBC News/Survey Monkey poll released Tuesday.

The billionaire businessman is supported by 35 percent of Republican and GOP-leaning registered voters in the online survey, with Sens. Ted CruzRafael (Ted) Edward CruzCruz says Cambridge Analytica assured him its practices were legal Dem battling Cruz in Texas: ‘I can understand how people think this is crazy’ Overnight Tech: Facebook faces crisis over Cambridge Analytica data | Lawmakers demand answers | What to watch for next | Day one of AT&T's merger trial | Self-driving Uber car kills pedestrian MORE (Texas) and Marco RubioMarco Antonio RubioRubio: McCabe 'should've been allowed to finish through the weekend' For Tillerson, bucking Trump became a job-killer At least six dead after pedestrian bridge collapses on cars in Florida MORE (Fla.) at 18 percent and 13 percent, respectively.

All other candidates poll in single digits, with retired neurosurgeon Ben Carson at 9 percent, former Florida Gov. Jeb Bush at 6 percent, New Jersey Gov. Chris Christie at 4 percent and businesswoman Carly Fiorina at 3 percent.

A third of white evangelicals surveyed, 33 percent, support Trump, while Cruz gets 21 percent and Rubio 10 percent of that group, a key support group candidates are focusing on in the early voting state of Iowa.

Trump is also supported by 35 percent of "very conservative" voters, versus 30 percent for Cruz and 8 percent for Rubio.

The poll comes about a month out from votes being cast in the race in the Iowa causes Feb. 1, where Cruz is the favorite to win, and the New Hampshire primaries Feb. 9, where Cruz and Rubio poll behind Trump.

Cruz and Rubio have largely avoided attacking Trump and have focused their barbs on each other recently, duking it out on the issue of national security and immigration heading into the next debates later this month.

On the Democratic side of the field, Hillary ClintonHillary Diane Rodham ClintonKoch-backed group launches six-figure ad buy against Heitkamp Trump keeps up 'low IQ' attack on Maxine Waters GOP leaders to Trump: Leave Mueller alone MORE leads Sen. Bernie SandersBernard (Bernie) SandersAnti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight Overnight Defense: Senate sides with Trump on military role in Yemen | Dem vets push for new war authorization on Iraq anniversary | General says time isn't 'right' for space corps MORE (I-Vt.) 53 percent to 36 percent, with just 2 percent of registered and leaning Democrats supporting former Maryland Gov. Martin O'Malley.

The survey of 3,700 adults nationally was conducted Dec. 28 through Jan. 3 with an overall margin of error of 1.9 points. The margin of error for the 949 GOP registered voters surveyed is 3.7 points and 3.3 points for the Democrats.