They may still be embroiled in a contentious primary race, but Democratic voters appear to want Hillary Clinton and Bernie Sanders to run on the same presidential ticket later this year.

A new Rasmussen Reports national telephone survey finds that from a list of five potential vice presidential picks, 36% of Likely Democratic Voters think Sanders should be Clinton’s running mate. Massachusetts Senator Elizabeth Warren comes in a distant second with 19%, while 10% prefer Housing and Urban Development Secretary Julian Castro.

Eight percent (8%) of Democrats think Clinton should tap New Jersey Senator Cory Booker for the VP spot, while just two percent (2%) say that of former Maryland Governor Martin O'Malley who dropped out of the 2016 Democratic presidential race in the early going. However, 12% of Democrats prefer some other candidate not listed, and 13% are undecided. (To see survey question wording, click here.)

Sign up: Free daily newsletter Sign up!

Among all Likely Voters, Sanders is still the favorite with 26%, followed by Warren with 13%. Booker and O’Malley each come in with six percent (6%), while Castro is the favorite of five percent (5%). But 44% of voters are looking elsewhere, including 25% who prefer some other candidate and 19% who are not sure.

Seventy-eight percent (78%) of all voters say the vice presidential nominee will be important to how they vote in the upcoming presidential election, but that includes only 33% who say it is Very Important. Seventy-seven percent (77%) of Democrats consider the veep spot to be important to their vote, compared to 85% of GOP voters. Still, GOP voters (34%) are slightly less likely than Democrats (37%) to say the candidate in the number two slot is Very Important.

(Want a free daily e-mail update? If it's in the news, it's in our polls). Rasmussen Reports updates are also available on Twitter or Facebook.

The survey of 1,000 Likely Voters was conducted on May 11-12, 2016 by Rasmussen Reports. The margin of sampling error is +/- 3 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.

On the Republican side, former House Speaker Newt Gingrich and former presidential candidate Dr. Ben Carson are early favorites among GOP voters to run alongside presumptive nominee Donald Trump.

Because of the anti-establishment tone of Trump's and Sanders' campaigns, some have suggested that they should reach outside their party for a running mate, but voters strongly disagree. Sixty-eight percent (68%) say it’s at least somewhat important for a presidential candidate to pick someone from his or her own party to be the vice presidential candidate, including 35% who say that’s Very Important. Thirty percent (30%) don’t think it’s important, including only six percent (6%) who say it’s Not At All Important.

Republicans (50%) are far more likely than Democrats (32%) and voters not affiliated with either major party (21%) to think it’s Very Important for a presidential nominee to choose within the party.

Twenty-six percent (26%) of unaffiliated voters think Sanders should be Clinton’s vice presidential pick, while 10% prefer Warren. However, nearly half of these voters prefer someone else or are not sure.

Most Republicans don’t prefer any of the candidates listed, but Sanders still leads the pack among GOP voters with 15%.

Forty percent (40%) of voters under 40 think Sanders should be Clinton’s running mate, a view shared by just 21% of middle-aged voters and 17% of senior citizens. Though Sanders draws the most support in all three age groups, those 40 and over are more likely to prefer another candidate to any of those listed.

Interestingly given the heavy media coverage about Sanders’ struggles to gain their support, black voters (34%) feel even more strongly than white voters (22%) do that Sanders should be Clinton’s running mate. An even higher number (42%) of other minority voters support Sanders on the ticket with Clinton.

Despite the surprising success of Sanders, Democrats remain overwhelmingly convinced that Clinton is their party's likely presidential nominee for 2016.

The success of Sanders in the 2016 campaign has exposed the growing rift between the Democratic party establishment and the party’s more progressive wing. Forty-seven percent (47%) of Democrats believe the Democratic Party should be more like Clinton, but 39% say it should be more like Sanders. Twelve percent (12%) say the party should be like neither one.

Warren is perhaps just as popular as Sanders on the political left, but only 30% of Democrats last August thought the Massachusetts senator should have run for the Democratic presidential nomination in 2016. Forty-five percent (45%) said she shouldn’t run.

So far the Clinton-Trump race looks like it’s going to be a close one.

Additional information from this survey and a full demographic breakdown are available to Platinum Members only.

Please sign up for the Rasmussen Reports daily email update (it’s free) or follow us on Twitter or Facebook. Let us keep you up to date with the latest public opinion news.