Joe Biden holds a commanding lead over Sen. Bernie Sanders in Arizona, according to a new poll released on the eve of that state’s presidential primary.

A Monmouth University survey released on Monday shows the former vice president with 51 percent support among likely Democratic presidential primary voters. Sanders – the populist lawmaker from Vermont who’s making his second straight White House run – stands at 31 percent. That's 20 percentage points behind Biden.

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Arizona joins Florida, Illinois and Ohio in holding Democratic nominating contests on Tuesday. As of now, officials in all four states plan to proceed with their primaries despite much of the country closing down as the coronavirus outbreak spreads. Polls in all four states indicate Biden holding double-digit leads.

Rep. Tulsi Gabbard of Hawaii – the only other remaining candidate left in the battle for the Democratic nomination – is backed by just 1 percent.

In the Biden-Sanders face-off, the poll indicates Sanders with at 48-41 percent edge among Latino voters and a large 56-28 percent lead among voters under age 50. But Biden holds a large 29-point lead among white voters and an overwhelming 48-point lead among voters age 50 and older.

“Biden has a strong advantage going into the primary. This is because much of his support has already been banked in the early vote. The closure of many polling places due to COVID-19 means it is uncertain how many voters who planned to vote on Tuesday will actually show up,” Monmouth University Polling Institute director Patrick Murray said in a statement.

The poll suggests that just over half of likely primary voters have already cast ballots, with Biden holding a nearly two-to-one margin over Sanders among those voters.

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Looking ahead to the November general election, the survey shows Biden with a slight 46-43 percent advantage over President Trump – while the Republican incumbent has a slight 44-43 percent edge over Sanders.

Trump topped 2016 Democratic nominee Hillary Clinton by 4 points in Arizona four years ago – and the state’s considered to be one of a handful of battleground states in the 2020 election.

The Monmouth University poll was conducted March 11-14, with 847 registered voters – including 373 likely to vote in the Democratic presidential primary – questioned by live telephone operators. The survey’s overall sampling error is 3.4 percentage points, with a margin of error of 5.1 percentage points for Democratic primary questions.