It detracts nothing from Barack Obama's achievement to note that his historic electoral success rests atop the epic political failure of George W. Bush. If Obama is shrewd enough, there's a lesson for the new president in the failure of the old one.

Bush and his chief political strategist, Karl Rove, dreamed of cementing a lasting Republican electoral majority. Instead, Bush has left his party in rubble.

The 2008 election represented a final grade on Bush's bruising and polarizing political strategy. To a degree unmatched by modern presidents, Bush governed more by mobilizing his base than by reaching out to voters and interests beyond it. His legislative strategy centered on minimizing dissent among congressional Republicans; his electoral strategy revolved around maximizing his vote among Republicans and conservative independents. On both fronts, his guiding principle was deepen, not broaden.

Only the most culturally conservative areas remain reliably red.

Through Bush's first term, that approach generated undeniable successes. The congressional Republican majority, demonstrating levels of party unity unequaled since around 1900, passed key elements of his agenda. A skillfully engineered surge in Republican turnout powered his re-election and GOP congressional gains in 2002 and 2004.

But through Bush's second term, this insular strategy grew unsustainable. By targeting so many of his policies toward the priorities of his conservative base, Bush ignited volcanic opposition from Democratic voters and steadily alienated independents. Because he had done so little to court voters beyond his ardent core, he lacked a well of good will to draw on when events turned against him, first with Katrina and Iraq, later with the economy. His disapproval rating soared to heights unsurpassed in modern polling.

That ferocious dissatisfaction fueled the Democratic recapture of Congress in 2006 by stampeding independent voters in their direction. Discontent with Bush again provided a huge tailwind for Democrats this week. Exit polls showed that a breathtaking 71% of voters Tuesday disapproved of Bush's performance. Two-thirds of them voted for Obama. That in itself effectively sealed the election against John McCain.

The pattern was similar in the states where Democrats captured Republican Senate seats: Exit polls showed that about two-thirds or more of voters who disapproved of Bush voted for winning Democrats in North Carolina, New Hampshire, Oregon, Virginia, New Mexico and Colorado. McCain and other GOP candidates made plenty of their own mistakes. But discontent with Bush was the gravity in this election -- the irresistible force that McCain and so many other Republicans could never escape.

Bush's polarizing method of governing will likely reverberate for Republicans far beyond these immediate losses. His approach has severely narrowed his party's electoral reach. Young people moved steadily away from the GOP under Bush and cast two-thirds of their votes for Obama. Likewise, Obama carried two-thirds of Hispanics and won comfortably among independents, reinforcing their Democratic tilt from 2006. And Obama reached 47 percent among white voters with college or post-graduate degrees -- which keyed his game-changing routs in white-collar suburbs from Pennsylvania to Colorado. McCain dominated only among working-class white voters, many of them culturally conservative and hawkish, but they represented just 39 percent of voters -- down from a majority as recently as 1992.

For Republicans, the geographic trends are even more ominous. The Southern evangelical face that Bush placed on his party accelerated the long-term GOP decline in the Northeast: Obama easily carried all 11 states from Maryland to Maine. Republicans now hold just four (of 22) Senate seats in those states and 17 (of 92) House seats, severe declines from as recently as 2002. In the Mountain West, Obama captured three states that backed Bush in 2004. Before 2004, Democrats held just three (of 16) Senate seats and seven (of 28) House seats across the eight-state region. After Tuesday, the numbers were seven and 17.

Under Bush, Democrats also solidified their hold on the West Coast (where they now hold all six Senate seats) and upper Midwest; now they are advancing in outer South states like Virginia and North Carolina, where Democratic House and Senate gains accompanied Obama's breakthrough victories Tuesday. Only the most culturally conservative areas -- the Deep South, Great Plains, rural Midwest and upper Rockies -- remain reliably red.

Bush can't be blamed for all of the GOP's distress. He sensibly sought to court Hispanics with comprehensive immigration reform (though he myopically retreated when congressional conservatives resisted). But by focusing his agenda so intently on the center of his coalition, Bush lost the center of the country. That's the cautionary lesson Obama will overlook at his peril.

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