WASHINGTON (CNN) As candidates for the Democratic nomination for president in 2020 begin to declare their intentions, a handful of potential candidates hold on to most of the early support, according to a new CNN poll conducted by SSRS, and Texas Congressman Beto O'Rourke is a new addition to the top tier.

Former Vice President Joe Biden continues to top the list when the potential Democratic electorate is asked who they'd be most likely to support for the nomination, with 30% saying they would back him. Vermont Sen. Bernie Sanders lands in second with 14%. Support for each is about the same as in October. O'Rourke lands in third with 9%, up 5 points since October. New Jersey Sen. Cory Booker follows at 5%. California Sen. Kamala Harris and Massachusetts Senator Elizabeth Warren have each dropped 5 points since October and are now below 5% support.

None of the other 14 possible candidates tested hits 5% support.

More than a year out from any primaries or caucuses and with most candidates undeclared, there are few meaningful demographic or political differences in the nomination race. One that helped define the 2016 battle for the Democratic nod between Hillary Clinton and Sanders continues on, with Sanders garnering much more support among younger voters (22% among those under age 45) than he gets among the older crowd (7% of those age 45 and up back him).

Read More