Former Vice-President Joe Biden is favored to win the 2020 Democratic nomination according to oddsmakers. Betting site Betonline.ag lists Biden's odds at +300.

Vermont Sen. Bernie Sanders and South Bend Mayor Pete Buttigieg both have the second-best odds at +400. Massachusetts Sen. Elizabeth Warren has the third-best odds at +500.  

Other contenders include businessman Andrew Yang (+600) and former New York Mayor Michael Bloomberg (+900).

The Democratic field has 15 candidates entering the Iowa caucuses in February.

President Trump could be the underdog once Democrats rally around a candidate. BetOnline gives Democrats the better odds of winning the general election, at -130, in comparison to Republican odds of +110. 

Trump is currently facing impeachment but it's unlikely that he will be removed. He is likely to be impeached by the House and acquitted by the Senate.

But as the incumbent, he has advantages, especially with fundraising.

Since World War II, the only incumbents that lost their re-election bid were George H.W. Bush in 1992, Jimmy Carter in 1980 and Gerald Ford in 1976. 

Trump has been suffering from a likeability issue since the beginning of his presidency. His approval rating has consistently been below 50% since February 2017, likely due to numerous controversies and scandals.