The modern Republican Party has for years boasted of being a “big tent,” sheltering everyone from Nelson Rockefeller to Pat Buchanan. But the party’s most grizzled veterans privately admit that it’s been stitched together as much by accidents of history as by ideological cohesion: the Cold War and resulting anti-Communism in the 1960s and 1970s, the magnetic personality of Ronald Reagan in the 1980s, the dubious morality of Bill Clinton in the 1990s. Most recently, as veteran Republican pollster Tony Fabrizio has said, “September eleventh and the war on terror glued the coalition together.”

But as discontent with the Iraq war rises and the Republican base begins to question some of the tactics being used in the fight against terrorism, that glue is dissolving, and the party risks breaking into many factions: social conservatives, moral conservatives, economic populists, economic supply-siders, deficit hawks, isolationists and realists, neoconservatives, libertarians. Diverging opinions within the party about the appropriate size of government only magnify that risk.

Since the beginning of the twentieth century, the party controlling the White House in the sixth year of a presidency has almost always suffered electoral losses—a phenomenon the political theorist Kevin Phillips has described as the “six-year itch.” As the Bush presidency enters its sixth year, Republicans in Washington suffer from leadership vacuums (see the House Republicans), scandal (see Duke Cunningham and Tom DeLay), rancorous ideological spats (see the failed Harriet Miers Supreme Court nomination), and simple voter fatigue.

Politics is famously local—especially in a non-presidential-election year. But this year, Republicans at the state level appear beset by infighting and logistical problems that mirror the ones in Washington. By our count, nine state Republican parties have leadership vacuums, five are mired in scandal, nine are in the throes of ideological clashes, and thirteen have fallen victim to Republican fatigue (from base supporters tiring of Bush’s leadership to swing voters questioning the merits of GOP dominance). Several of these newly fragile Republican machines—Ohio’s and Florida’s especially—will bear watching not just this year, but in the run-up to 2008.

Of course, as measured by political time, 2008 is still epochs away. And another accident of history may yet keep this Republican coalition from disintegration: her name is Hillary Clinton.