Former Vice President Joe Biden Joe BidenOmar fires back at Trump over rally remarks: 'This is my country' Trump mocks Biden appearance, mask use ahead of first debate Trump attacks Omar for criticizing US: 'How did you do where you came from?' MORE is leading a new CNN poll of Democrats and Democratic-leaning independents that also shows increasing support for Sen. Kamala Harris Kamala HarrisButtigieg stands in as Pence for Harris's debate practice First presidential debate to cover coronavirus, Supreme Court Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (D-Calif.).

Biden, who has yet to enter the Democratic presidential race, is out in front with 28 percent of those polled. In second place is Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.), who is backed by 20 percent of voters.

But support for Harris in the poll has jumped to 12 percent, an 8-point increase since the most recent edition of the poll was released in December.

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Following Harris is former Rep. Beto O’Rourke (D-Texas) at 11 percent. O’Rourke launched his presidential campaign last week.

No other candidate received double-digit support in the poll. Sen. Elizabeth Warren Elizabeth WarrenHarris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda Judd Gregg: The Kamala threat — the Californiaization of America GOP set to release controversial Biden report MORE (D-Mass.) is in fifth with 6 percent of support, according to the poll.

Biden's support dropped from 30 percent to 28 percent, while Sanders's support rose from 14 percent to 20 percent.

O'Rourke also saw a two-point climb from the last poll, while Warren went up from 3 percent to 6 percent.

Former Secretary of State John Kerry John Forbes KerryThe Memo: Warning signs flash for Trump on debates Divided country, divided church TV ads favored Biden 2-1 in past month MORE (D), who has yet to enter the race, gets 4 percent, while Sen. Cory Booker Cory Anthony BookerBipartisan praise pours in after Ginsburg's death DHS opens probe into allegations at Georgia ICE facility Democratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility MORE (D-N.J.), who is in the race, has 3 percent.

A more centrist candidate, Sen. Amy Klobuchar Amy KlobucharSocial media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE of Minnesota (D), also gets 3 percent.

No other candidate in the race has more than 1 percent. That group includes Sen. Kirsten Gillibrand Kirsten GillibrandSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Suburban moms are going to decide the 2020 election Jon Stewart urges Congress to help veterans exposed to burn pits MORE (D-N.Y.), Rep. Tulsi Gabbard Tulsi GabbardRepublicans call on DOJ to investigate Netflix over 'Cuties' film Hispanic Caucus campaign arm endorses slate of non-Hispanic candidates Gabbard says she 'was not invited to participate in any way' in Democratic convention MORE (D-Hawaii) and former Colorado Gov. John Hickenlooper (D).

Those results are based based on interviews with 456 Democrats and Democratic-leaning independents between March 14 and March 17. The margin of error is 5.7 percentage points.

The CNN poll also found that 40 percent of respondents are "extremely enthusiastic" about voting for president in 2020. The enthusiasm is higher among Republicans, with 57 percent of self-identified Republicans responding that they are "extremely enthusiastic," compared to 46 percent of Democrats and 26 percent of independents.

The full CNN poll was based on interviews with 1,003 adults between March 14 and March 17. The full sample has a margin of error of 3.8 percentage points.

The majority of Republicans also said they think the GOP should nominate President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE in 2020, with 76 percent saying Trump should be the nominee and 19 percent saying a different candidate should be nominated.