WASHINGTON — When Jeb Bush decides whether to run for president, there will be no family meeting à la Mitt Romney, no gathering at Walker’s Point in Kennebunkport to go over the pros and cons. “I don’t think it’ll be like a big internal straw poll,” said his son, Jeb Bush Jr.

But if there were, the results of the poll are pretty much in. As Mr. Bush nears a decision to become the third member of his storied family to seek the presidency, the extended Bush clan and its attendant network, albeit with one prominent exception, are largely rallying behind the prospect and pulling the old machine out of the closet.

“No question,” Jeb Jr. said in an interview, “people are getting fired up about it — donors and people who have been around the political process for a while, people he’s known in Tallahassee when he was governor. The family, we’re geared up either way.” Most important, he added, his mother, Columba, the prospective candidate’s politics-averse wife, has given her assent.

Within the family, the top cheerleaders have been George H. W. Bush and George W. Bush, both of whom know something about running for president, and both of whom have an interest in perpetuating, if not redeeming, the family legacy. Barbara Bush, the former first lady and Jeb Bush’s mother, is unconvinced, according to people close to the family, but has been persuaded to stop saying it so publicly. George P. Bush, his other son, who is running for Texas land commissioner, has been supportive of what he calls a likely run.