When Bill Clinton and his family were preparing to spend their first presidential vacation on this secluded island in 1993, a 7-year-old islander shared her concerns.

“Please tell Chelsea’s Mom about ticks,” she wrote in a letter to the Vineyard Gazette. “It is important for Chelsea to be checked every day.”

This weekend, as “Chelsea’s Mom” returns to this favored vacation spot, she will find islanders in a similarly protective mood.

“It is a place that feels very affectionate toward” the Clintons, said Lynn Forester de Roths­child, a longtime supporter who will co-host a fundraiser for Hillary Rodham Clinton’s presidential campaign Sunday. “And they return the favor.”

The Clintons are not the only famous parents in town: Sasha and Malia’s rather well-known mother and father are already vacationing here. Presidents past, current and possibly future could rub shoulders Saturday night, when they are all expected to attend an 80th-birthday party for Vernon Jordan, a trusted friend of both families.

No official meeting is scheduled, and the two families are unlikely to swap deck chairs or restaurant recommendations. Yet, given the island’s history of mixing sandcastles with politics, it was almost inevitable that at some point this August, Martha’s Vineyard would become a symbolic stop in the lengthy baton-passing between current president and potential Democratic nominee.

For a relatively small island, measuring just 96 square miles, an unusual concentration of politicians, journalists and liberal intellectuals has long decamped here every summer, setting up a veritable Washington-on-the-Sea, at least for Democrats.

Republican Ulysses S. Grant was the first president to escape the humidity of the District for the natural air conditioning of the ocean here in 1874, and chief executives of all stripes came for years after. But since the 1970s, the island has tilted well to the left: The debate here is not which party but which leader.

The Clintons and the Obamas have stuck to this tradition, with both families choosing to vacation here almost every summer of each presidency. This weekend, Hillary Clinton will rely on the island not only for support but as a casual, ideologically friendly spot to relax with a few like-minded folks.

Last time she ran for the nomination, islanders bucked the trend in the rest of Massachusetts, backing Obama in the 2008 primary by a comfortable margin. Even so, the Clintons are “extremely well thought-of” here, said Ronald Rappaport, a prominent island lawyer who will also be a guest at Jordan’s party. The 2008 vote was “despite the loyalty and affection towards Hillary,” he insisted, and was due largely to her stance on Iraq.

In addition, this place in summertime has in abundance something even more useful to Clinton than support: money. Forester de Rothschild is at the head of a long line of Vineyard donors with weighty checkbooks.

The chief executive of the family investment company works between homes in London and the Vineyard but is devoting as much time as possible to the campaign.

“This is a do-or-die time, so we are giving it our all,” she said.

Sunday’s fundraiser, a “conversation with Hillary” at the home of Frank Biondi, a former Viacom chief executive, and his wife, Carol, will set “friends” back $1,000, while “champions” can pay $2,700 for, among other things, the chance to pose with the candidate for a photograph.

There is yet another reason Clinton and Obama have sought out the island: subtlety. A few residents appear at the end of long driveways to cheer the presidential motorcade as it meanders through the woods, but politicians, like celebrities, are largely left alone here.

Arriving in Vineyard Haven on Friday, former president Bill Clinton was spotted wandering along Main Street and browsing a bookshop. He shook a few hands but went largely undisturbed.

Sunday’s fundraiser will reflect this casual approach, complying with the Vineyard’s unofficial dress code of polo shirt and salmon shorts.

“There won’t be a tie to be seen,” Forester de Rothschild said.

All this dressing down can be deceptive: Many of those topping off their tans here have far higher IQs than the average beachgoer. “It’s very relaxed, but people don’t come here and shut down their brain,” Forester de Roths­child said.

Hillary Clinton’s visit is expected to be far shorter than the president’s — she is due in Las Vegas on Tuesday — but on previous trips she has hardly lacked potential dinner companions. The island’s “summer people” include academics and Pulitzer Prize-winning journalists.

A Ralph Waldo Emerson quotation adorns the wall of one coffee shop, while the Edgartown bookstore has sold out of most political biographies. Only two copies of Clinton’s “Hard Choices” remain on the shelves, not far from “Pearls, Politics and Power: How Women Can Win and Lead,” by Madeleine Kunin, a former governor of Vermont.

Vineyard Gazette columnist Skip Finley says there is another reason both first families keep coming back, as legions of Democrats did before them. They feel at home, says Finley — who has lived here year-round for 16 years — because of the racial diversity of the summer visitors and the island’s tolerance.

From the president down, scores of African Americans travel here every summer, while the place regularly hosts African American film festivals and lectures about race.

“There’s a large group of highly motivated, well-educated black people,” Finley said. “If you’re looking for that utopia, then you have that here.”

Whatever inspires the Clintons to come, that first trip, back in 1993, was certainly a success. At the end of their 10-day stay, the family wrote an open letter to islanders.

“We look forward to visiting Martha’s Vineyard again some day,” read a version published at the time in the Vineyard Gazette. “Not only to enjoy the island but the island people.”

And they did, year after year.

Of course, the next Democrat in the White House — whenever he or she is elected — could always break the habit.

But don’t count on it.