In 2001, Dean published The Rehnquist Choice: The Untold Story of the Nixon Appointment that Redefined the Supreme Court, an exposé of the White House's selection process for a new Supreme Court justice in 1971, which led to the accession of William Rehnquist to the United States' highest court. Three years later, Dean authored a book heavily critical of the administration of George W. Bush, entitled Worse than Watergate, which called for the impeachment of Bush and Vice President Dick Cheney for allegedly lying to Congress.
His subsequent book, released in summer 2006, is titled Conservatives without Conscience, a play on Barry Goldwater's book The Conscience of a Conservative. In it, he asserts that post-Goldwater conservatism has been co-opted by people with authoritarian personalities and policies, citing data from Bob Altemeyer. According to Dean, modern conservatism, specifically in the Christian Right, embraces obedience, inequality, intolerance, and strong intrusive government, in stark contrast to Goldwater's philosophies and policies. Using Altemeyer's scholarly work, he contends that there is a tendency toward ethically questionable political practices when authoritarians are placed in positions of power, and that the current political situation is dangerously unsound because of it. Dean cites the behavior of key members of the Republican leadership, including George W. Bush, Dick Cheney, Tom DeLay, Newt Gingrich, and Bill Frist, as clear evidence of a relationship between modern right-wing conservatism and this authoritarian approach to governance. He places particular emphasis on the abdication of checks and balances by the Republican Congress, and of the dishonesty of the conservative intellectual class in support of the GOP, as a result of the obedience and arrogance innate to the authoritarian mentality.
After it became known that George W. Bush authorized NSA wiretaps without warrants, Dean asserted that Bush is "the first President to admit to an impeachable offense". On March 31, 2006, Dean testified before the Senate Judiciary Committee during hearings on censuring the president over the issue. Senator Russell Feingold (D-Wis.), who sponsored the censure resolution, introduced Dean as a "patriot" who put "rule of law above the interests of the president." In his testimony, Dean asserted that Richard Nixon covered up Watergate because he believed it was in the interest of national security. This sparked a sharp debate with Republican South Carolina senator Lindsey Graham, who repeatedly asserted that Nixon authorized the break-in at Democratic headquarters. Dean finally replied, "You're showing you don't know that subject very well." Spectators laughed, and soon the senator was "sputtering mad".
Dean's 2007 book Broken Government: How Republican Rule Destroyed the Legislative, Executive and Judicial Branches is, as he wrote in its introduction, the third volume of an unplanned trilogy. In this latest book, Dean, who has repeatedly described himself as a Goldwater conservative, built on Worse Than Watergate and Conservatives Without Conscience to argue that the Republican Party has gravely damaged all three branches of the federal government in the service of ideological rigidity and with no attention to the public interest or the general good. Dean concludes that conservatism must regenerate itself to remain true to its core ideals of limited government and the rule of law.
In 2008, Dean co-edited Pure Goldwater, a collection of writings by the 1964 Republican presidential nominee and former U.S. Senator from Arizona Barry Goldwater, in part as an act of fealty to the man who defined his political ideals. His co-editor was Goldwater's son Barry Goldwater, Jr.
In the 1979 TV mini-series, Blind Ambition, Dean was played by Martin Sheen. In the 1995 film, Nixon, directed by Oliver Stone, Dean was played by David Hyde Pierce. In the 1999 film Dick, Dean was played by Jim Breuer.
Dean frequently served as a guest on the former MSNBC and Current TV news program, Countdown with Keith Olbermann, and The Randi Rhodes Show on Premiere Radio Networks.
Historian Stanley Kutler was accused of editing the Nixon tapes to make Dean appear in a more favorable light.
On September 17, 2009, Dean appeared on Countdown with new allegations about Watergate in hand. He stated that he had found information via the Nixon tapes, that showed what the burglars were after: information on a kickback scheme involving the Democratic National Convention in Miami, Florida. Dean also asserts that Nixon did not directly order the break-in, but that it was ordered by Ehrlichman on behalf of Nixon.
In speaking engagements during 2014, Dean called Watergate a "lawyers' scandal" that, for all the bad, ushered in needed legal ethics reforms.