Former Vice President Joe Biden, 2020 Democratic presidential candidate, speaks during a campaign event in Columbus, Ohio, U.S., on Tuesday, March 10, 2020.

Former Vice President Joe Biden leads Sen. Bernie Sanders in two of Tuesday's four primaries as he looks to build a delegate lead his rival cannot overcome, according to NBC News/Marist polls released Monday.

In Ohio, Biden garners 58% of support among likely Democratic primary voters, compared with 35% for Sanders, I-Vt.

Biden has a smaller but still significant lead over Sanders in Arizona. He gets 53% of support among likely voters in Tuesday's contest, while Sanders comes in at 36%.

Ohio awards 136 pledged delegates. Arizona allocates 67.

Florida and Illinois, two of the largest states in the country, will also hold primaries.

Heading into the day's contests, Biden leads Sanders 860 to 706 in the pledged delegate race. A candidate needs to reach a 1,991-delegate majority to win the Democratic nomination and take on President Donald Trump in November.

Wins by wide margins in three or four of the states voting Tuesday could all but seal the primary for Biden. He has also led recent surveys of Florida and Illinois.

The NBC News/Marist polls also gauged potential general election matchups in Ohio and Arizona, key 2020 swing states. In Ohio, Biden and Sanders lead Trump by 4 and 2 percentage points, respectively.

The former vice president has a 1 percentage point edge over the incumbent in Arizona. Sanders trails Trump by 3 percentage points.

Arizona also plays host to one of this year's most important Senate races, as Democrats hope to unseat Republican Sen. Martha McSally in their quest to win a majority in the chamber. Democrat Mark Kelly, a former astronaut, leads the incumbent by a 48% to 45% margin, according to the NBC/Marist poll.

The Ohio poll, conducted from March 10-13, surveyed 1,710 registered voters with a margin of error of plus or minus 2.9 percentage points. It polled 486 likely Democratic voters with a margin of error of plus or minus 5.6 percentage points.

The Arizona poll, conducted from March 10-15, surveyed 2,523 registered voters with a margin of error of plus or minus 2.7 percentage points. It polled 523 likely Democratic voters with a margin of error of plus or minus 6 percentage points.

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