A new Monmouth University poll shows former Vice President Joe Biden leading Sen. Bernie Sanders, I-Vt., by 20 percentage points in the state ahead of its presidential primary on Tuesday and holding a slim lead over President Donald Trump in the general election.

Among Arizonan voters likely to vote in the Democratic primary on Tuesday, 51% said they would vote for Biden, and 31% for Sanders. One percent of those surveyed said they would vote for Rep. Tulsi Gabbard, D-Hawaii, the sole remaining major candidate in the race besides Sanders and Biden.

The former Vice President maintains a large lead in delegates, with 890 delegates currently pledged to Sanders' 736. Gabbard has two pledged delegates.

Biden held leads among groups that made up a larger proportion of the electorate like voters over the age of 50 and white voters, whereas Sanders beat Biden among Latino voters and voters under 50, both of which are smaller proportions of the electorate.

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The coronavirus pandemic could upend the state's primary by adding uncertainty to the number of voters who would go in person to the polls on Tuesday, said Patrick Murray, director of the Monmouth University Polling Institute.

“Biden has a strong advantage going into the primary. This is because much of his support has already been banked in the early vote," Murray said in a statement on the survey results. "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.”

The Monmouth University Polling Institute polled 847 registered Arizonan voters from March 11 to 14 by telephone, and 373 likely Democratic primary voters. Questions asked of all registered voters have a margin of error of 3.4 percentage points, and questions asked of Democratic primary voters have a margin of error of 5.1 percentage points.

Over half of all primary voters said they had already voted, and among the early voters, Biden led them 50% to 27% for Sanders.

The poll also spelled trouble for Sen. Martha McSally, R-Ariz., who is up for reelection this November. The poll showed Democratic challenger Mark Kelly, a retired astronaut, beating McSally by 6 percentage points, 50% to 44%, among all registered voters surveyed.

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President Donald Trump won Arizona in 2016, but the poll found him with a net negative favorability rating in the state and narrowly trailing Biden in the state's general election.

When polled about a hypothetical general election matchup, Biden beat Trump by 3 percentage points among all registered voters, 46% to 43%. Trump polled ahead of Sanders by one percentage point, or 44% to 43%.

Fifty percent of the Arizonans in the survey had an unfavorable opinion of Trump, and 41% had a favorable opinion of him.