A poll released Monday shows Bernie Sanders is the top presidential choice among progressives, an important bloc of voters in a second bid for the Democratic nomination in 2020.

In another poll of progressives, the Vermont senator comes in third in a tight race with former Vice President Joe Biden and Texas Rep. Beto O'Rourke.

And the democratic socialist ranks seventh in a third poll among another key group, with Sen. Kamala Harris of California the "overwhelming early favorite."

Finally, Biden holds a double-digit lead over Sanders in Iowa, where the first-in-the-nation caucus presents the first major test for presidential hopefuls in 2020.

In the final weeks of 2018, the only sure news the polls brought Sanders is that he will need to cut a path through a pack of formidable rivals in 2020.

Sanders, along with most of the likely top Democratic contenders, has yet to formally announce their candidacy. But for many potential candidates, the announcement is seen largely as a formality.

More:VT Insights: 5 signs Bernie Sanders is running in 2020

MoveOn.org straw poll

On Dec. 11, MoveOn.org released the results of a straw poll among the progressive organization's members showing Sanders third with 13.1 percent of the vote, behind O'Rourke, 15.6 percent, and Biden, 14.9 percent.

O'Rourke rose to national prominence for his youthful energy and fundraising prowess in his surprisingly competitive challenge to Republican Sen. Ted Cruz this year.

More:VT Insights: Are Bernie Sanders, Joe Biden too old to run in 2020?

MoveOn members said next president should "inspire the public with deep progressive values" and "make the connections between racial, social, and economic injustice."

Democracy for America Presidential Pulse Poll

The Democracy for America poll released Dec. 18, scrambles the MoveOn.org results placing Sanders on top with 34.1 percent, followed by Biden with 14.9 percent and O'Rourke with 12.3 percent.

In a news release, Yvette Simpson, incoming Chief Executive Officer of Democracy for America, wrote, "These results make clear that, while Bernie Sanders' has a strong early lead, no single potential presidential candidate has full command of the Democratic Party's progressive base heading into 2019."

She the People straw poll

Sanders failed to makes the top five in a straw poll of top three presidential candidates conducted Nov. 29 to Dec. 13 for She the People, "a national network of influential women of color in politics."

Coming in first was Harris with 71.1 percent of the vote, followed by O'Rourke, 38.3 percent, and Biden, 25 percent. The Vermont senator came in seventh with 12.1 percent of the vote.

In 2016, failure to win over a large number of African American voters proved to be a significant weakness for Sanders.

More:VT Insights: Joe Biden visiting home turf of likely 2020 rival Bernie Sanders

The She the People poll also asked, "Which candidate(s) would you not consider for the 2020 Presidential nominee based on their inability to appeal to or reach women of color voters?"

Sanders came in third with 32.2 percent, behind Michael Avenatti, 43.2 percent, and Michael Bloomberg, 37.8 percent.

Des Moines Register/CNN/Mediacom Iowa Poll

The Des Moines Register/CNN/Mediacom Iowa Poll released Dec. 15 showed Biden with a big lead over second place Sanders, 32 percent to 19 percent. O'Rourke was third with 11 percent.

More:Iowa Poll: Biden, Sanders top early look at possible Democratic hopefuls in 2020 caucuses

Ann Selzer, president of Selzer & Co., the firm that conducted the Iowa poll, told the Des Moines Register that Sanders and Biden benefit from name recognition.

She added, "If Bernie Sanders taught us anything in 2016, it’s that you can start with nothing and do everything but win."

Aki Soga is insights and engagement editor for the Burlington Free Press. Email him at asoga@freepressmedia.com