Four years ago, in the week after the 2004 presidential election, we were working furiously to put the finishing touches on the book we coauthored, "It's My Party Too: The Battle for the Heart of the GOP and the Future of America."

Our central thesis was simple: The Republican Party had been taken hostage by "social fundamentalists," the people who base their votes on such social issues as abortion, gay rights and stem-cell research. Unless the GOP freed itself from their grip, we argued, it would so alienate itself from the broad center of the American electorate that it would become increasingly marginalized and find itself out of power.

At the time, this idea was roundly attacked by many who were convinced that holding on to the "base" at all costs was the way to go. A former speechwriter for President Bush, Matthew Scully, who went on to work for the McCain campaign this year, called the book "airy blather" and said its argument fell somewhere between "insufferable snobbery" and "complete cluelessness." Gary Bauer suggested that the book sounded as if it came from a "Michael Moore radical." The National Review said its warnings were "at best, counterintuitive," and Ann Coulter said the book was "based on conventional wisdom that is now known to be false."

What a difference four years makes -- and the data show it.

While a host of issues were at play in this election, the primary reason John McCain lost was the substantial erosion of support from self-identified moderates compared with four years ago. In 2004, Democratic nominee John Kerry held a margin of just 9 percentage points over President Bush among moderate voters. This year, the spread between Barack Obama and McCain was 21 points among this group. The net difference between the two elections is a deficit of nearly 6.4 million moderate votes for the Republicans in 2008.

In seven of the nine states that switched this year from Republican to Democratic, Obama's vote total exceeded the total won by Bush four years ago. So even if McCain had equaled the president's numbers from 2004 (and he did not), he still would have lost in Colorado, Florida, Iowa, Nevada, New Mexico, North Carolina and Virginia (81 total electoral votes) -- and would have lost the election. McCain didn't lose those states because he failed to hold the base. He lost them because Obama broadened his base.

Nor did the Republican ticket lose because "values voters" stayed home. On the contrary, according to exit polls, such voters made up a larger proportion of the electorate this year than in 2004 -- 26 percent, up from 23 percent. Extrapolating from those data, McCain actually won more votes from self-identified white evangelical/born-again voters than Bush did four years ago -- 1.8 million more. But that was not enough to offset the loss of so many moderates.

Following the conventional wisdom of the past two presidential elections, McCain tried mightily to assuage the Republican Party's social-fundamentalist wing. His selection of Alaska Gov. Sarah Palin, whose social views are entirely aligned with that wing, as his running mate was clearly meant to demonstrate his commitment to that bloc. Yet while his choice did comfort those voters, it made many others uncomfortable.

Palin has many attractive qualities as a candidate. Being prepared to become president at a moment's notice was not obviously among them this year. Her selection cost the ticket support among those moderate voters who saw it as a cynical sop to social fundamentalists, reinforcing the impression that they control the party, with the party's consent.

In the wake of the Democrats' landslide victory, and despite all evidence to the contrary, many in the GOP are arguing that John McCain was defeated because the social fundamentalists wouldn't support him. They seem to be suffering from a political strain of Stockholm syndrome. They are identifying with the interests of their political captors and ignoring the views of the larger electorate. This has cost the Republican Party the votes of millions of people who don't find a willingness to acquiesce to hostage-takers a positive trait in potential leaders.

Unless the Republican Party ends its self-imposed captivity to social fundamentalists, it will spend a long time in the political wilderness. On Nov. 4, the American people very clearly rejected the politics of demonization and division. It's long past time for the GOP to do the same.

Christine Todd Whitman, who served as administrator of the Environmental Protection Agency from 2001 to 2003, is cochair of the Republican Leadership Council. Robert M. Bostock, a freelance speechwriter, was her coauthor for the book "It's My Party Too." They wrote this article for the Washington Post.