It’s not often that a politician edged out in a closely fought election decides, upon reflection, that he got what he deserved. But that is what Lincoln Chafee, former Republican senator from Rhode Island, grudgingly acknowledges at the end of his unusually candid memoir, Against the Tide: How a Compliant Congress Empowered a Reckless President. As the subtitle suggests, despite his reputation as mild-mannered and friendly, Chafee, who served in the Senate from 1999 through 2006, the year a wave of anti-Bush sentiment swept away the Republican majority in Congress, has not written a feel-good, conciliatory book. He has written a searing indictment of how his fellow Republicans disgraced themselves by bowing to the Bush Administration’s extremist demands, from the perspective of a moderate who came to feel deeply estranged from the party to which he once felt loyally bound. The people who voted to unseat Republicans like him in the 2006 midterm election “did what they had to do to check the Bush-Cheney agenda,” Chafee writes. The Congress in which he served “deserves the infamy that history will surely assign it.”

The fact that Chafee feels this way is, some on the right will undoubtedly contend, hardly surprising: Chafee, they’ll tell you, was always a liberal in disguise, the Senate’s number-one RINO (Republican in Name Only), as the magazine Human Events once labeled Chafee, who had it in for the Bush Administration from day one.

It’s an accusation Chafee probably wishes were true. But reality is more complicated and sheds light on how profoundly the party has changed over the course of a generation. As Chafee confesses early in his book, in 2000 he supported George W. Bush in the Rhode Island presidential primary. What he saw in the Texas governor was a pragmatist who, like his father, George H.W. Bush, would be open to compromise and willing to disappoint the GOP base if circumstances demanded it. Chafee could not have been more wrong, of course, but the proclivity to see in the son a mirror image of the father, and to envisage him as something other than a bumbling ideologue, was somewhat understandable in light of his own background. Chafee entered the Senate after his father, John Chafee, a four-term senator, died suddenly of heart failure. The elder Chafee belonged to the once-sizable bloc of so-called Rockefeller Republicans: socially tolerant, fiscally conservative moderates who did not regard cutting taxes as a sacred mission, did not sneer at every government program they came across and did not assume anyone who disagreed with them was morally suspect.

Chafee had convinced himself that a similar spirit might prevail under the younger Bush. He quickly learned otherwise. The day after the Supreme Court handed Bush the presidency by halting the Florida recount, Chafee relates in his book, Dick Cheney dropped by for a closed-door lunch with the handful of moderate Senate Republicans. As Cheney ticked off the incoming Administration’s priorities–disavowing the Kyoto Protocol, canceling the Anti-Ballistic Missile Treaty, ramming through a $1.6 trillion tax cut–Chafee realized that all the talk of Bush being a “uniter” had been a sham. He also realized that Republicans of his father’s ilk were no longer treated with even a modicum of respect (“Cheney was not asking for support–he was ordering us to provide it”). And they seldom stood up for themselves: instead of voicing objections to the Vice President-elect’s “shockingly divisive” agenda, his colleagues nodded obsequiously. “Mr. Cheney tore our best campaign promises to shreds and the moderates acquiesced instead of pelting him with outrage,” Chafee angrily recalls. “It was the most demoralizing moment of my seven-year tenure in the Senate.”

In fairness to the targets of his criticism, Chafee did some acquiescing of his own through the years. Unlike former Vermont Senator James Jeffords, he was not so disgusted with the Administration that he was prompted to leave the party. Some of the worst legislation of the Bush era–the Patriot Act, the 2005 bankruptcy bill–garnered his support, and he refrained from taking a clear stand against some of the White House’s most reckless ideas, such as privatizing Social Security. To his credit, though, Chafee did resist subscribing to certain articles of faith. To the fury of groups like the Club for Growth, he refused to support Bush’s tax cuts. And to the rage of the religious right, he opposed a constitutional amendment to ban gay marriage and was one of only three GOP senators to oppose the Partial Birth Abortion Ban, which many Democrats supported. In 2002 he was also the only GOP senator to vote against the Iraq War resolution.

That none of this was acceptable to the guardians of political correctness on the right reminds us that the key litmus test during the Bush era was not loyalty to conservative principles; it was loyalty to the White House. Chafee’s book makes this clear. For as he takes pains to emphasize, he opposed the Iraq War not because he is a liberal pacifist but because he concluded that launching a messianic war on the basis of flimsy evidence would undermine stability in a volatile part of the world, a position many conservative realists shared. He voted against Bush’s tax cuts not because he is a left-leaning populist but because “deep down, the fiscal conservative in me said no.” Chafee found the Administration’s suspension of habeas corpus and violation of the Fourth Amendment ban on unwarranted wiretapping alarming–but aren’t conservatives supposed to be suspicious of big government? He opposed amending the Constitution to prevent states from passing laws on gay marriage–but isn’t this the natural position for supporters of states’ rights? He was wary of entrusting politicians to make intimate decisions for women rather than allowing women to make those decisions themselves–but is that a liberal or a conservative view?

There was a time not long ago when such questions could at least be debated in the Republican Party without provoking charges of heresy. Chafee, who finally did switch his affiliation from Republican to independent last year, appears to realize that those days are gone. Reached by phone at Brown University, where he now teaches, he said that he is even considering voting for Barack Obama in the upcoming primary, not least because Obama, unlike Hillary Clinton and John McCain, had the wisdom to oppose the Iraq War. (In his book, Chafee is scathing about Democrats who caved on the war.) He did not sound surprised about the conservative fracture over the potential nomination of McCain, who is reviled on the right for the rare times he didn’t follow White House orders.

To those who celebrated the political style that triumphed in the age of Bush–what Chafee tartly describes as “rightwing groupthink on every issue”–the news of Chafee’s departure from the GOP was no doubt welcome. And the charges he levels in his book will undoubtedly be dismissed as sour grapes. To those who want to understand why Republicans no longer control Congress, and why the reasonable voices in the GOP have grown ever fainter in recent years, following the arc of his career will prove both depressing and illuminating.