MILTON -- The big blue house on Adams Street with the wide front porch and green decorative moldings is part of living history.
On Thursday, one of its former occupants will watch his son take the oath of office as president for the second time.
George H. W. Bush, whose birthplace is on the corner of Adams and Hutchinson streets, probably won't be thinking of his former home in Massachusetts when he watches his son, George W., take his Texas-sized strides to the podium. Nor is he likely to think of clapboard churches and fall foliage when he gazes over at his second son, Governor Jeb Bush of Florida, his Mexican-born daughter-in-law, Columba, and their proudly Hispanic son George P. Bush.
But the Bush family's journey from New England to the Sun Belt marked a watershed in American politics that no one comprehended even 15 years ago, when George the elder was president. Still distantly influenced by the Yankee tradition of noblesse oblige, the Bushes have come to represent a microcosm of national political and demographic shifts. Their changing faces have become, to some degree, America's family portraits.
The transformation began with George H. W. Bush's move to Texas in 1948, which placed the Bushes in the jet stream of economic change. Bush was representing a holding company run by his father's closest friend, and the fusion of East Coast contacts and Western deal-making created its own political dynamic, one that historians are beginning to recognize.
''What makes the Bushes unique among political dynasties is the lack of any particular place -- you go where the action is," said Bruce Buchanan, a government professor at the University of Texas.
''They represent a kind of ambition, seeking opportunities to prove themselves. There's a potency to that."
Political scientists once attacked the Bushes as lacking a distinct political viewpoint analogous to Ronald Reagan's conservatism or Lyndon Johnson's liberalism, but the rise of the current President Bush and Governor Bush has revealed one common thread, a tendency for change in ways that broaden their identity and their political appeal.
''In going to Texas they sort of reinvented themselves," said Robert Dallek, author of best-selling biographies of John F. Kennedy and Johnson. ''Texas was one of those frontiers where you could do that."
In the decades after George H. W. Bush took a job with the oil-equipment company Ideco and moved to Odessa, Texas, the Sun Belt grew more quickly than other parts of the country. Size had always been part of the Texas mystique, but from 1950 until last year its share of the national population swelled from 5.1 percent to 7.7 percent. Florida, the eventual home of Jeb Bush, made a bigger jump, from 1.8 percent in 1950 to 5.9 percent last year.
Meanwhile, Massachusetts dropped from 3.1 percent of the national whole in 1950 to 2.2 percent last year, and seemed to fall further out of step with the national zeitgeist, from car racing to cuisine.
The Bushes probably sensed the coming changes. They knew they were leaving a shrinking pool to swim in much larger waters, but were in no danger of drowning: East Coast connections would be more valuable in the growing Sun Belt.
After a brief stint in Odessa, the Bushes lived in California before returning to Midland, Texas, which was attractive to Easterners in the oil business.
Still, there were cultural hurdles to overcome. George's wife, Barbara, remembered her husband putting on a pair of Bermuda shorts and then scrambling home to change because truck drivers were whistling at him.
''I don't believe he ever wore shorts again, except to play tennis," she wrote in her memoir.
But while Texas made its mark on Bush, he carried his own template for success, and it was forged in New England. Just like his father, Prescott Bush, he spent his early years making money through family contacts and then used his business ties to seed a political career.
Prescott Bush had served two terms as senator from Connecticut and George H. W. Bush ran twice for the Senate from Texas and lost. Texas politics in the 1960s was a stew of progressivism and conservatism, of hostility toward civil rights laws and friendliness toward New Deal-style social programs. Ideology didn't track along party lines.
Democrats were dominant, but badly split over civil rights. Bush, running as a Barry Goldwater-style Republican against liberal Ralph Yarborough in 1964, tried to peel away right-leaning Democrats. Six years later, after a successful House career, he went for the Senate again against conservative Democrat Lloyd Bentsen. Running as more of a Nixon-era progressive, he tried to peel away liberals.
Each time, he ran a respectable campaign and lost, lacking the instinctive rapport with voters.
But when Bush first ran for president, in 1980, after a string of appointive offices in the 1970s, his awareness of Texas politics held him in good stead. Cast by some as representing the faded ''Rockefeller wing" of the GOP, Bush nonetheless adopted enough conservative positions on issues like abortion to be chosen as Reagan's vice presidential nominee.
That opened the door to his own presidency eight years later and put his sons George W. and Jeb in positions to compete for major offices afterward.
For most of US history, political dynasties, even those that extended to the White House, have been brands with distinct appeal to a state, like the Tafts of Ohio and the Kennedys of Massachusetts. When relatives moved elsewhere, like Patrick Kennedy to Rhode Island, they were extending the family brand of politics to a like-minded state.
The Bushes, however, are less a brand than a seal of approval. George H. W. Bush strayed from his father's liberal Republicanism in his first runs in Texas, but his father stood loyally by. And when George W. and Jeb ran for office in 1994, their father wrote each urging them to go their own ways and not to worry about his feelings when ''they compare you to a Dad for whom English was a second language and for whom the word 'destiny' meant nothing," as recounted in ''The Bushes," by Peter Schweizer and Rochelle Schweizer.
George W., whose different temperament was announced by his Texas twang, took his father literally. His subsequent career can be viewed as a reaction to his father's: Where the elder Bush said he wanted the presidency for ''the honor of it all," George W. brags that he came to Washington to get things done; where his father was said to lack guiding principles, George W. proclaims that ''you know where I stand"; and where his father refused to take over Baghdad for fear of chaos, George W. professes to be undeterred by the Iraqi insurgency.
''I generally don't like it when people delve into pop psychology, but with the last two presidents, boy, I think you can go a long way with pop psychology," said Daron Shaw, a former Bush campaign aide in 2000 who is now an associate professor of government at the University of Texas.
But father, sons, and any future Bush politicians still drink from the same well of family contacts; cataloged in computer records and numbering in the hundreds of thousands, Bush friends fuel all the family's candidacies.
''I've inherited all my father's enemies and half of his friends," George W. said during the 2000 campaign. But he seems to have had it backward: His father's friends mostly stuck by him, and his father's enemies gave him a fresh look.
Likewise, were the family mantle to be passed from George W. to Jeb, even the president's enemies might see the brainy younger brother as a corrective, a more open-hearted, policy-oriented version of his older kin. And the Spanish-speaking Jeb comes equipped with a familial appeal to the fastest-growing demographic in politics: Hispanics, whose numbers surged from 6.5 percent of the national population in 1980 to 12.5 percent in 2000.
Whether Jeb will ever be president is a question in the minds of political scientists: Buchanan, the UT professor, speculates that much will depend on his brother's performance in the second term. Dallek, the author, warns of America's inbred resistance to monarchy. Shaw suggests the next Bush president might not be Jeb but, after a suitable interlude, Jeb's dashing son George P., who campaigned for his uncle (''mi tio") on Spanish-language television.
''If he wants it, he's going to have major opportunities," said Shaw of the 28-year-old George P., who practices law in Dallas. ''Looks do matter, and style matters."
So does family history, especially, as Shaw pointed out, if the family assumes some of the functions of an old-fashioned political party without tethering a candidate to one brand of politics.
Kennedy-style liberalism has waned, and other dynasties like the Rockefellers and Roosevelts have unraveled, but the Bushes are at a peak of power, their homes and birthplaces and presidential libraries being enshrined in American history.
In Milton, the big pewter-colored house on Adams Street still offers testimony to the social order that once sustained the ambitions of a high-minded elite. But historians agree that the plaque in front, and the tiny American flag affixed to it, honor a new elite based on the formidable power of reinvention.