By JOHN F. HARRIS & CAROL E. LEE | 1/20/10 6:16 PM EST

As the Obama administration marks its first birthday, there is no reason to shop around for the perfect present. What President Barack Obama needs most is obvious: a new political strategy — ideally one more grounded in the realities of governance than the one he embraced a year ago Wednesday.

Republican Scott Brown’s astonishing Senate victory in Massachusetts does not spell doom for Obama’s agenda, even if many Democrats are acting as though it does. He remains a president who scores more than 50 percent in most polls and whose party controls Congress. That’s more than enough clout for an ambitious president to dominate Washington.

But Massachusetts marked the final, crushing piece of evidence against the theory of the case that animated Obama’s first year. Simply put, that theory — which made some sense a year ago — turned out to be wrong.

Specifically, it was wrong on three major counts:

• Obama and his team believed that the 2008 election represented something seismic — in other words, something fundamental and long-lasting — in the country’s governing landscape. They believed that the historical cycle had turned, that voters had not only rejected George W. Bush’s brash conservatism but also moved beyond Bill Clinton’s tepid and defensive-minded progressivism.

The nation’s problems and mood put momentum behind Obama’s vision of robust, large-scale government action. But there had been no seismic shift. The country’s ideology is fluid — and depends on perceptions of the economy and the daily flow of news out of Washington. The assumption that Obama would be swimming mostly with the current rather than often against it on issues such as health care, financial regulation and global warming was naive in retrospect.

• Obama believed that early success would be self-reinforcing, building a powerful momentum for bold government action. This belief was the essence of the White House’s theory of the “big bang” — that success in passing a big stimulus package would lead to success in passing health care, which in turn would clear the way for major cap-and-trade environmental legislation and “re-regulation” of the financial services sector — all in the first year.

This proved to be a radical misreading of the dynamics of power. The massive cost of the stimulus package and industry bailouts — combined with the inconvenient fact that unemployment went up after their passage — meant that Obama spent the year bleeding momentum rather than steadily increasing public confidence in his larger governing vision. That vision was further obscured for many Americans by the smoke from the bitter and seemingly endless legislative battle on Capitol Hill over health care.

• Most devoutly of all, the Obama team believed that there was something singular about the president’s appeal and ability to inspire.