Washington (CNN) A new national poll finds Sen. Bernie Sanders is well ahead of the field of Democratic presidential candidates as the party's nominating process nears the fourth contest of this cycle.

There is no prior trend from CBS News and YouGov on the national Democratic race, but Warren's 19% showing appears to be an improvement compared with other polls conducted before last week's debate in Nevada. In an Ipsos/Reuters poll, which uses a similar online survey methodology, she stood at 9% in polling conducted from February 14 through 17.

The poll also found that nearly two-thirds of registered voters nationwide say they think President Donald Trump probably or definitely will get reelected (65% say so, 35% say that probably or definitely will not happen), even as hypothetical matchups with the top Democratic candidates are tight regardless of who the Democratic nominee is: The margin was 3 points or less in each of six matchups tested.

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