GREAT FALLS, Va. — What happens if you're a Republican commentator and you write a book critical of President Bush that gets you fired from your job at a conservative think tank?

For starters, no other conservative institution rushes in with an offer for your analytical skills.

"Nobody will touch me," said Bruce Bartlett, author of the forthcoming "Impostor: Why George W. Bush Bankrupted America and Betrayed the Reagan Legacy." "I think I'm just kind of radioactive at the moment."

Mr. Bartlett, a domestic policy aide at the White House in the Reagan administration and a deputy assistant treasury secretary under the first President Bush, talked last week at his suburban Washington home about his dismissal, his book and a growing disquiet among conservatives about Mr. Bush.

Although "Impostor" is flamboyant in its anti-Bush sentiments — on the first page Mr. Bartlett calls Mr. Bush a "pretend conservative" and compares him to Richard Nixon, "a man who used the right to pursue his agenda" — its basic message reflects the frustration of many conservatives who say that Mr. Bush has been on a five-year federal spending binge. Like them, Mr. Bartlett is particularly upset about Mr. Bush's Medicare prescription drug plan, which is expected to cost more than $700 billion over the next decade.

He is unhappy, too, with the president's education and campaign finance bills and his proposal to overhaul the nation's immigration laws, which many Republicans call a dressed-up amnesty plan. The book, to be published by Doubleday on Feb. 28, also criticizes the White House for "an anti-intellectual distrust of facts and analysis" and an obsession with secrecy.

"The Clinton people were vastly more open and easier to deal with and, quite frankly, a lot better on the issues," Mr. Bartlett said in the interview, in the kitchen of his pared-down modern house on a street of big new homes in Great Falls. Mr. Bartlett hastened to add that although he admired Mr. Clinton's economic policies, that did not mean he had changed sides.

"I haven't switched to the Democratic Party," he said. "I wrote this for Republicans."

One Republican, Scott McClellan, the White House press secretary, responded to Mr. Bartlett's book by e-mail over the weekend. "Spending is coming under control," Mr. McClellan wrote, adding that in the 2007 budget submitted to Congress earlier this month, "the president put forward the most disciplined non-security discretionary proposal since the Reagan era."

Mr. Bartlett is well regarded in conservative circles, even as the tone of his book has made him a maverick.

"Bruce is really an exception, not the rule, in the degree and thoroughness of his discontent," said William Kristol, a conservative strategist and the editor of The Weekly Standard. "So I wouldn't make too much of it. On the other hand, one thing I've noticed giving speeches in the last couple of months is that conservatives remain pro-Bush, but the loyalty to the movement and the ideas is deeper than the personal loyalty now. Two years ago, Bush was the movement and the cause."

Mr. Bartlett, 54, the author of a syndicated newspaper column and articles in academic journals, was dismissed in October as a senior fellow at the National Center for Policy Analysis, a research group based in Dallas. In the interview, Mr. Bartlett said he had been fired because his increasingly critical comments about Mr. Bush, in his column, in his book and in other publications, had hampered the ability of the research institution to raise money among Republican donors.

He also provided a copy of an e-mail message that he said was sent to him in August 2004 by Jeanette Goodman, the vice president of the research institution. "100K is off the table if you do another 'dump Cheney' column and 65K donor is having a rebuttal done, in a national magazine, to your attack on the fair tax people so that 65K may be gone also," Ms. Goodman wrote about one of Mr. Bartlett's columns about the vice president. "Do you have any ideas on where I could raise that amount quickly?"

John C. Goodman, the president of the organization and Ms. Goodman's husband, said in a telephone interview over the weekend that he did not know what his wife had said to Mr. Bartlett and that he did not want to say whether Mr. Bartlett "did or didn't hurt fund-raising." But Mr. Goodman added, "That's not why he was fired."

Mr. Goodman said he dismissed Mr. Bartlett because after reading the manuscript of "Impostor" last fall, he determined that Mr. Bartlett had reneged on an agreement not to personalize his criticism of the president or any other individual, in the Bush administration or not. "He was supposed to write a book on policy," Mr. Goodman said.

Mr. Bartlett, for his part, said he was fine financially but hoped his book would be a best seller. In any case, he is tired of think tanks.

"Some reporter called the other day and asked me about the budget," Mr. Bartlett said. "It's just a boring subject. It's never changed in the 30 years I've been working on the budget. But if I were still working for a think tank, I'd have to be up on that kind of stuff and ready to give a quote or some intelligent analysis, and I feel I can kind of ignore some of that."

So what now?

"I've been thinking about writing a history of the Democratic Party," Mr. Bartlett said. "It kind of seemed an interesting thing for a Republican to do."