The results of a 2020 poll out Sunday underscore how undecided Democrats and left-leaning independents are about who should be the Democratic Party's standard bearer.

CNN released a survey, conducted by SSRS, showing former Vice President Joe Biden as their candidate of choice to challenge President Trump in two years. Biden got 33 percent of the vote when 464 Democrats and Democratic-leaning independents were asked in a telephone survey from Oct. 3-7.

The next-closest contender is Sen. Bernie Sanders, I-Vt., who was 20-percentage points back with 13 percent.

Despite the huge gap, the results display a sizable lack of excitement around a single candidate which was evidence four years ago. Compare this year's CNN poll with the same one taken at around the same time in 2014: Hillary Clinton was the clear favorite by a lot. She got 65 percent of the vote from Democrats and left-leaning independents, way ahead of second place -- Sen. Elizabeth Warren, D-Mass., who got 10 percent.

One notable factor to consider this time around is a much wider field of potential candidates, including senators, mayors, and outsider candidates emboldened by Trump's rise, including Michael Avenatti, lawyer to porn star Stormy Daniels (he got only 1 percent in the new poll).

Though Biden is the clear front-runner, an issue voters may have to grapple with is that the former vice president may not even run in 2020. Just last week he downplayed speculation, saying he's not running for president "at this point." He has also said that he won't officially make up his mind until after the 2018 midterm elections.

Meanwhile, Trump, whose poll numbers are up after a contentious fight over the successful confirmation of Supreme Court Justice Brett Kavanaugh, has signaled that he is eager to face off against Biden, saying over the summer "I dream about Biden" running.

The CNN poll out Sunday shows Americans increasingly more convinced Trump will win re-election (46 percent to 47 percent saying he'll lose).

Another takeaway from the polling shows big progress for liberal heavyweight Sanders, who ran a competitive campaign for the Democratic presidential nomination in 2016. He is up 8 percentage points in CNN's latest poll, up to 13 percent, which is a significant improvement over the 5 percent he got four years ago.