Poll: Sanders, Biden seen as most popular second choices in Dem primary

Former Vice President Joe BidenJoe BidenPoll: Bloomberg stalls after Vegas debate Bloomberg campaign: Vandalism at Tennessee office 'echoes language from the Sanders campaign and its supporters' Democratic strategist says Biden 'has to' get second place in Nevada MORE and Sen. Bernie SandersBernie SandersPoll: Bloomberg stalls after Vegas debate Prominent Texas Latina endorses Warren Bloomberg campaign: Vandalism at Tennessee office 'echoes language from the Sanders campaign and its supporters' MORE (I-Vt.) are the most popular potential Democratic presidential candidates, but they are also the top second choices among registered voters, according to a Morning Consult survey released this week.

The poll found that Sanders was the second choice for 27 percent of Biden's supporters. Another 15 percent of Biden supporters said they would back Sen. Kamala HarrisKamala Devi HarrisHouse to vote on legislation to make lynching a federal hate crime Overnight Energy: EPA to regulate 'forever chemicals' in drinking water | Trump budget calls for slashing funds for climate science centers | House Dems urge banks not to fund drilling in Arctic refuge Democratic senators criticize plan that could expand Arctic oil and gas development MORE (D-Calif.) while 9 percent said they supported Sen. Elizabeth WarrenElizabeth Ann WarrenPoll: Bloomberg stalls after Vegas debate Bloomberg unveils billboards to troll Trump ahead of campaign stops John Legend joining Warren in South Carolina next week: report MORE (D-Mass.).

Among Sanders's supporters, 26 percent said they supported Biden as a second choice, followed by Warren at 16 percent and Harris at 7 percent.

Warren and Sanders both hail from the progressive wing of the Democratic Party, while the poll showed some crossover between those supporting Biden and Harris.

Among Harris's supporters, 20 percent said they would choose Biden as a second choice, while Sanders was not among the top picks as a backup option. And among Biden supporters, 15 percent said they would support Harris as a second choice.

However, Sanders registered strongly as a second choice for Warren's supporters, with 25 percent saying the Vermont senator and 2016 runner-up for the Democratic nomination was a backup for them, followed by Harris at 14 percent and Biden at 13 percent.

Among former Rep. Beto O'RourkeBeto O'RourkeCNN signs Andrew Yang as contributor Krystal Ball: Voters are coming to their own judgements about who is electable Warren campaign to host series of events in Texas MORE's (D-Texas) supporters, 20 percent said they would pick Sanders as a second option, while 18 percent chose Biden. 

O'Rourke has yet to announce whether he will run for president next year, though has been mulling a bid.

The poll comes as speculation around potential 2020 runs from Biden and Sanders heats up. 

The Hill reported on Thursday that sources familiar with the former vice president's plans say that he is almost certain to enter the 2020 fray.  

Yahoo News reported late last month that Sanders would announce his second presidential bid in the near future.

Warren formally launched her White House bid last weekend, while Harris entered the race late last month.

The Morning Consult poll was conducted from Feb. 4-10 among 11,627 registered voters. The survey's margin of error is plus or minus 1 percent. 

— Julia Manchester