MONTPELIER >> Barack Obama easily won the 2008 Vermont primary over Hillary Clinton, 59 percent to her 39 percent, but Bernie Sanders could win his home state by an even bigger margin.
Retired Middlebury College political science professor Eric Davis estimated Sanders likely would get between 60 and 75 percent of the vote on the Democratic side.
Primary voters in Vermont are asked to choose just one of the major parties' ballots and then select candidates from that ballot. The ballots were finalized in January and some candidates have dropped out since then.
The Republican ballot lists 10 candidates, five of whom are still running: Donald Trump, Marco Rubio, Ted Cruz, John Kasich and Ben Carson. The Democratic ballot has four candidates: Hillary Clinton, Bernie Sanders, Martin O'Malley and Roque "Rocky" De La Fuente. O'Malley has suspended his campaign, while De La Fuente's website was still urging people to vote for him March 1.
Polls open between 5 and 10 a.m., depending on the city or town; all polls close at 7 p.m.
Tuesday's presidential primaries are being held separately from primaries for other state and federal offices, which are scheduled for Aug. 9. Those races will determine party nominees for U.S. Senate, U.S. House, governor and other state offices.
Recent polling puts Trump ahead of the GOP field in Vermont, and Sanders way out in front of Clinton among Democratic voters.
Sanders got 71 percent when he won re-election to the Senate in 2012, beating Republican John MacGovern of Windsor.
In 2008, the last time there wasn't an incumbent president seeking re-election, nearly 196,000 Vermonters voted in the primary, with nearly four times as many taking the Democratic ballot featuring Obama and Clinton as taking the Republican one.
The home-state advantage was in effect when former Gov. Howard Dean sought the Democratic presidential nomination in 2004. Dean's campaign was fading in most of the country by March, but he won easily in Vermont over the eventual nominee, John Kerry.
Clinton has received the endorsements of Sen. Patrick Leahy, Gov. Peter Shumlin and former Govs. Madeleine Kunin and Howard Dean. Sanders has been endorsed by U.S. Rep. Peter Welch and by both of the candidates vying for the Democratic gubernatorial nomination: Matt Dunne and Sue Minter.