Vineyard election officials are expecting a record turnout for Tuesday’s election following a rush of new voter registrations and a huge number of absentee ballots already cast.

The number of absentee ballots as of yesterday was in some cases close to twice that normally seen at a presidential election, a sure sign, Island town clerks said, of an engaged electorate, and a likely indicator of an unprecedented turnout.

Just since January, the number of voters Island-wide has grown by almost 600 and the number of registered Democrats has jumped 358, an increase of 8.4 per cent.

The number of registered Republicans has declined over the same period by 77, or two per cent.

Democrats now outnumber Republicans by 4,592 to 1,429 — though the largest proportion of voters, 6,622 of the total of 12,662, remains unenrolled.

All the indicators point to a substantial majority for the Democratic presidential ticket of Barack Obama and Joseph Biden over the Republican ticket of John McCain and Sarah Palin.

Not only are there more than three times as many registered Democrats, but they appear more energized. The turnout for the February primaries was an early indicator of this. Hundreds of registered Republicans did not bother to vote, while the number who voted for one or other of the Democratic contenders — 4,948 — exceeded by some 700 the number registered for the party.

Election officials also note an unusually large number of young voters — a demographic which breaks strongly for Sen. Obama.

“In 2004, we had 400 absentee votes,” said Oak Bluffs assistant town clerk Laura Johnston just after noon yesterday. “So far we’ve had 485 this time, and there are more coming in all the time.

“We’ve never seen anything like this. And we are also seeing a lot of young and first-time voters,” said Ms. Johnston.

Karen Medeiros in the town clerk’s office in Edgartown, said by noon yesterday, 378 absentee ballots had already had been received, compared with about 200 in a usual presidential election.

In Aquinnah about a quarter of the 400 registered voters had already voted.

“We have now about 95 absentee votes, and I expect it will go over 100,” said town clerk Carolyn Feltz.

There appeared to be a correlation between the proportion of registered Democrats in the various Island towns and the number of early votes.

Aquinnah is the most Democratic of all the Island towns, by a margin of 130 to 15, and 25 per cent of votes were already in. Chilmark, the next most Democratic town — 366 to 74 — also had the second highest proportion of early voters, 168 at noon yesterday, or about 20 per cent.

But town clerks reported a surge of absentee voting everywhere. Tisbury town clerk Marion Mudge said she had received 375 by yesterday morning, compared with a previous record of about 300. And Prudy Whiting of West Tisbury said there had been 200 in-state absentee ballots and 21 overseas ballots. While she could not give a direct comparison with other years, she said: “It’s a lot. It’s big. And more people are still walking in all the time.”

The question, it seems, is not whether the Island will prefer the Democratic presidential team, but by how much. While there are no polls specific to the Island, the state of Massachusetts as a whole, according to the most recent average of published polls, preferred the Obama ticket by a margin of 23.7 per cent.

The real uncertainties on election day will be instead about the other ballot questions and about the election process itself.

Election officials across the Island and the state are concerned about the prospect of confusion on election day arising from a last-minute change to voting rules, of which they were notified only on Wednesday.

New legislation extends from six to 18 months the grace period under which voters who have moved within Massachusetts, but had not registered at their new address, may return to their previous municipality to vote.

But those voters will be limited to a partial ballot covering only the offices of President and Vice President, U.S. Senate and the three statewide ballot questions.

The change requires new ballot forms, yet to be printed and delivered, and comes with a complex four-page memorandum — sent out yesterday — detailing how the new ballots would be processed.

Local election officials see the last-minute changes as a recipe for confusion and delay, particularly given that so many people already have voted under the old regime, and that poll workers have not been instructed on the changes.

“I’m at a loss to understand why they’ve done this now,” said Ms. Mudge.

“For years the grace period has been six months. If you haven’t registered in your new town, you can go back to your prior place of residence for state elections and state primaries only.

“For some reason they have decided you should be able now to go back for up to 18 months.”

Of particular concern is the fact that voters with handicaps would be disadvantaged, because the auto-mark machine they normally use will not accept the new forms. Instead, the memorandum said, any voter who is handicapped and falls within the new rules would be given a regular ballot, which would then have to be set aside for later verification.

“Talk about ridiculous,” said Ms. Mudge, adding: “I am appalled that anyone would change regulations six days before an election.”

Apart from the presidency, there are five contested positions among the nine on the ballot.

Incumbent Cong. William Delahunt is unopposed, as is Carole Fiola for first district councillor and state Sen. Senator Robert O’Leary.

Elizabeth Herrmann of Edgartown is running unopposed for Dukes County register of probate. Noreen Mavro Flanders of Tisbury is running for county treasurer without contest.

U.S. Sen. John Kerry, a Democrat, faces two opponents: Republican Jeffrey Beatty and Libertarian Robert Underwood. State polls suggest Senator Kerry will win easily.

By contrast, the hotly contested race for Cape and Islands state representative looks anything but easy. There are four candidates: Daniel Larkosh, who won the Democratic primary, and Jacob Ferreira, Melissa Freitag and Timothy Madden, who all are unenrolled.

The race for Dukes County commission is a complicated contest with three candidates on the ballot and two write-ins. And Island voters will choose nine members of the Martha’s Vineyard Commission from 10 candidates, one of them a write-in.

There are also five ballot initiatives — six if you are a Tisbury voter.

Question One, if passed, would halve state income tax from 5.3 to 2.65 per cent beginning next year and eliminate it by 2011. Proponents say it would save the average taxpayer $3,700 per year and create thousands of jobs by encouraging new industry. Opponents say it would deprive the state of 40 per cent of its income, some $11 billion, and cripple vital services.

Question Two would replace the current criminal penalties for the possession of less than an ounce of marijuana with a civil penalty of $100. Offenders under 18 would also have to complete a drug awareness program. Proponents argue the current regime does little to stop marijuana use. Opponents favor strong law enforcement for marijuana possession.

Question Three would phase out greyhound racing. Proponents, including the MSPCA, believe the sport is inhumane. Opponents say the dogs are not treated poorly, and that as many as 1,000 jobs would be lost.

Question Four, the result of 18 months of work by a county charter study group, would reduce terms for county commissioners from four to two years.

In every town but Tisbury Question Five is a nonbinding resolution calling for universal single-payer health insurance in Massachusetts.

In Tisbury, Question Five relates to a Proposition 2.5 override to allow the town to pay for the cost of architectural and engineering services for a planned new emergency services facility.

In Tisbury, the universal health care question is Question Six.

Polls will be open in every Island town on Tuesday from 7 a.m. to 8 p.m. Polling places are as follows: Aquinnah, town hall; Chilmark, community center; Edgartown, Baylies Room (lower level), Old Whaling Church; Oak Bluffs, town library; Tisbury, American Legion Hall; West Tisbury, public safety building.