THE ACCIDENTAL AMERICAN: TONY BLAIR AND THE PRESIDENCY, by James Naughtie, Public Affairs, 250 pages, $26.

This groundbreaking book about Tony Blair — British prime minister for the past seven years — accomplishes at least three objectives:

• It treats at great length the "special relationship" promoted by American presidents and British prime ministers since World War II, when Franklin D. Roosevelt and Winston Churchill became both allies and fast friends.

• It looks in depth at the personality, principles and style of Blair — and is the first book to do so.

• And it examines the evolution of Blair from traditional leader to more "presidential" in the American style.

The author, a BBC news anchor, journalist and political historian, is well-equipped for the job. He is probably the most qualified expert on Tony Blair, and he presents an intriguing portrait of a political figure whose principles have been characterized as liberal or progressive, yet could forge an equally strong political and personal relationship with both Bill Clinton, a Democrat, and George W. Bush, a Republican.

In fact, the relationship with Bush has led to the most difficult chapter of Blair's political life — an American-British alliance making war on Iraq even when most members of his own Labour Party, the opposition Conservative Party and the general public were adamantly opposed.

Blair appears fiercely independent at home and subordi- nate to Bush at the same time. Naughtie discusses the progress of the relationship and the disagreements that were ironed out between the two men — always with Blair backing down.

The result is that Blair emerges as an enigma, someone who has stood for principle in the past, a people person who thinks on his feet, a charismatic leader with distinctive verbal skills, and yet willing to tag along with the United States at the very real risk of losing his job at home.

The fact that Blair would get along so well with Bush, a man who has been more interested so far in the use of power than in ideology, a man who is uncomfortable speaking from a podium or talking with the press, seems odd.

There are two keys, according to the author — one, that Bush believes strongly in the need to cultivate the "special relationship," and two, that Blair genuinely enjoys Bush's friendship.

But the most interesting and instructive point made here is the assertion that Colin Powell, secretary of state under Bush, has been strongly opposed to the tactics and approach taken by the administration with respect to Iraq. Powell, of course, has vehemently denied that to the American press.