People vote in the Super Tuesday primary at Wakefield High School on March 3, 2020 in Arlington, Virginia. (OLIVIER DOULIERY / AFP)

ARLINGTON, the United States - Polling stations opened on the US East Coast on Tuesday morning, kicking off the so-called "Super Tuesday" primaries of the 2020 presidential election.

After caucuses and primaries in four early voting states, Senator Bernie Sanders of Vermont is currently leading in the Democratic field

In Virginia, one of 14 US states scheduled to hold elections this day, only candidates running for the Democratic nomination for the White House are on the ballot, as the state's Republican Party has canceled its primary to throw full support behind sitting President Donald Trump.

Other states, including populous California and Texas, are scheduled to hold both Republican and Democratic primaries, some of which will begin hours later because of time differences.

Trump, who's facing no major opponents in his own party, is expected to win the GOP primaries, while on the Democratic side there are still five vying for the party's nomination to challenge the incumbent.

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After caucuses and primaries in four early voting states, Senator Bernie Sanders of Vermont is currently leading in the Democratic field with the most pledged delegates to the Democratic National Convention (DNC), followed by former Vice President Joe Biden.

Besides them, former New York City Mayor Michael Bloomberg, who's making his ballot debut, Senator Elizabeth Warren of Massachusetts, and US Congresswoman Tulsi Gabbard of Hawaii are also in the Democratic primary race.

At a polling station in Arlington, Virginia, Max Blake, a voter, told Xinhua that he had voted for Sanders, adding that he was aware of a tussle within the Democratic Party but believes they will eventually unite for the race against Trump.

During Super Tuesday, 1,357 pledged delegates to the DNC or a third of the total will be up for grabs.

To win the Democratic presidential nomination, a candidate must receive support from a majority of all the 3,979 pledged delegates on the first ballot of the national convention: 1,991 delegates.

In other words, the Super Tuesday primaries will not determine who will become the Democratic presidential nominee. However, Super Tuesday could offer indicators for how the rest of the primaries might play out.

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"This is the first time that a large number of states in different regions of the country all vote on the same day," Clay Ramsay, a researcher at the Center for International and Security Studies at the University of Maryland, told Xinhua.

"The four previous state caucuses and primaries each had their own local flavor. They can't tell us what Democrats across America are thinking," Ramsay said. "Super Tuesday will get us much closer to seeing that."