Few things reveal more about the shifting political geography of America over the past fifty years than the history of its most successful dynasty, the Bush family.

Prescott Bush, its great patriarch, was a Wall Street banker turned Republican US Senator who won election in 1952 when it was still politically fashionable, and viable, to be a north-eastern moderate. His grandson, George W Bush, was a southwestern conservative, in common with every other elected Republican president since the civil rights era.

The transitional figure, of course, was George Herbert Walker Bush: the Massachusetts-born Yale graduate who moved to Texas to dig for oil and to carve out a political career of his own. His journey speaks of that historically anomalous realignment: of how the power-base of the party of Abraham Lincoln crossed the Mason-Dixon line and came to be relocated in the southern Sun Belt.

For students of US politics, however, the more recent history of the Bush family tells a very different story about the current state of the GOP: the extent to which the party has been damaged by George W's two-term presidency, and how the former president is partly to blame for the weakness of the Republican field.

On its newly refurbished campaign website, the New Yorker recently published a light-hearted list of the five people conservatives should blame if Mitt Romney wins the nomination. It featured, in ascending order, Anthony Kennedy, the Supreme Court Justice who ruled in favour of allowing unlimited contributions to SuperPacs, the creation of which helped Romney defeat Newt Gingrich in Iowa and favours well-financed 'establishment' candidates.

Next came Barack Obama for appointing Jon Huntsman as his ambassador to China, a posting that undercut the former diplomat's campaign. In third position came Cheri Daniels, the wife of Mitch, the Indiana Governor, who is thought to have persuaded her highly-qualified husband not to run. Then came Michele Bachmann, the Minnesota Congresswoman whose victory in the Iowa straw poll in August last year forced Tim Pawlenty, another proven executive, from the race.

Pole position, however, was reserved for George W Bush. The reason? That he had failed to groom a conservative successor during his eight years in office. 'A successful Presidency can produce a new crop of future Presidential candidates for the party that controls the White House,' wrote Ryan Lizza. 'The Bush years had the opposite effect.' Dick Cheney. Donald Rumsfeld. Colin Powell. Paul Wolfowitz. They could hardly be described as coming men.

My sense is that the New Yorker fingered one of the right culprits but for the wrong reasons.

For a start, it seems unreasonable to expect an incumbent to mentor a potential successor given the ludicrous burdens of the modern-day presidency. That said, Condoleezza Rice, his National Security Advisor and Secretary of State, was once spoken of as a possible contender. Mitch Daniels also served for two years as his budget director.

Besides, state politics rather than Washington has been the main nursery of executive talent in recent decades. Four of the last five presidents – Bush 43, Bill Clinton, Ronald Reagan and Jimmy Carter – first caught the eye as successful governors.

No, there are more persuasive reasons why the president whose chief political strategist, Karl Rove, boasted about building a 'permanent Republican majority' has left the party in such poor repair. More on that in a follow-up post.

Photo courtesy of Wikipedia.