Sen. Bernie Sanders would defeat President Donald Trump by 11 points in a head-to-head match-up in 2020, the best among would-be Democratic challengers, according to the latest Zogby Analytics poll.

Former Vice President Joe Biden would defeat the president by nine points, according to Zogby's hypothetical poll.

Sanders, an independent who caucuses with Democrats, performed the best out of the four Democrats Zogby included in its survey, all of whom would nevertheless defeat Trump, according to Zogby.

Zogby's results:

Sanders: 51 percent; Trump: 40 percent.

Biden: 50 percent; Trump: 41 percent.

Michelle Obama: 47 percent; Trump: 44 percent.

Sen. Elizabeth Warren: 45 percent; Trump: 43 percent.

All of the hypotheticals have 9 percent undecided, except for Warren-Trump at 13 percent, according to Zogby.

Sanders would be 79 years old on election day 2020, and Biden would turn 78 two weeks after the election.

Zogby Analytics conducted the survey of 1,514 likely voters in the U.S. Oct. 19-25. Based on a confidence interval of 95 percent, the margin of error for 1,514 is 2.5 percentage points.