Here's a summary of the current national polling averages, as well as those in the four states that will hold their primary or caucus in February.
Joe Biden has a small lead over Bernie Sanders nationally, both are well out in front of the rest of the 12 person field. However, the picture becomes much less clear when looking at the states that kick off the 2020 election calendar. This is important for a couple reasons. First, delegates are won at the state level, not nationally. More importantly, because the primaries/caucuses occur over an extended period, each contest will be affected by the results in the ones that precede it.