Rumor in Martha’s Vineyard is that the Obamas will vacation there this summer, and residents are guessing that the first couple will head to State Road, in West Tisbury. The new locavore restaurant, from chef-owners Mary and Jackson Kenworth (who became beloved by Vineyarders when they owned the Sweet Life Café), is said to be backed by a powerful crew, including Comcast chairman Brian Roberts and former News Corp. president Peter Chernin and his wife, Megan, and was designed by the Obama-appointed White House decorator, Michael Smith. Callers trying to score a reservation are greeted by yet another bigwig with D.C. ties: That’s Vernon Jordan on the answering machine.