Hovering over ''Lincoln's Virtues'' is the shadow of another recent study, Lerone Bennett Jr.'s ''Forced Into Glory,'' a full-scale assault on Lincoln's reputation that paints him as a supporter of slavery and an inveterate racist. If Bennett's book is a somewhat intemperate prosecutor's brief, Miller offers the case for the defense.

Miller acknowledges that Lincoln opposed allowing blacks in Illinois to vote, hold office or intermarry with whites, and that he never called for repeal of the state's draconian Black Laws, which severely restricted the rights of the small black population. He points out in extenuation that most of Lincoln's racist statements were defensive responses to Democrats' far more overt and insidious appeals to racism. In the great 1858 Senate campaign, Lincoln's rival, Stephen A. Douglas, repeatedly insisted that blacks were not entitled to share in the inalienable rights cited in the Declaration of Independence. To this, Lincoln responded that blacks might not merit political equality but that the natural rights enumerated by Jefferson applied to all mankind.

Miller makes clear Lincoln's deep hatred of slavery. Regarding race, however, his defense is not entirely successful. Having earlier praised Lincoln for moral independence, he explains that when it came to blacks, Lincoln ''acquiesced in the racial prejudice by which he was surrounded.'' He insists, however, that Lincoln's inclusion of blacks within the Declaration of Independence was meant surreptitiously to subvert the philosophical underpinning not simply of slavery but of racism as well. The problem with this argument was pointed out half a century ago by Richard Hofstadter in his brilliant essay on Lincoln in ''The American Political Tradition.'' How could blacks exercise and defend their natural rights while denied the vote, the right to testify in court and access to education, as they were in Illinois?

Nor does Miller deal, except in passing, with Lincoln's nearly lifelong support for colonization. In his great Springfield speech of 1854, Lincoln asserted that he would prefer to send the slaves, if freed, ''to Liberia -- to their own native land'' (a phrase he used even though some blacks' ancestors had been in North America longer than his own). Lincoln's support of a policy that might be called the ethnic cleansing of America was no transitory fancy. He promoted it in numerous prewar speeches, two State of the Union addresses, several cabinet meetings and a notorious exchange with black leaders at the White House in 1862. Lincoln's bias should not blind us to his many virtues, yet it cannot be denied that, like many of his contemporaries, he held prejudiced views regarding blacks even as he believed that slavery was a crime.

Miller's discussion of race is the linchpin of a broader argument about politics and the possibilities of moral action. Among his purposes is to restore readers' respect for politicians, whose reputation has been tarnished by Vietnam, Watergate, Iran-contra and other examples of malfeasance in office. Lincoln was a professional politician. As a Republican leader, he worked to have the party focus on its most popular position -- opposition to the expansion of slavery -- and put aside divisive questions (like the repeal of the fugitive slave law, hostility to immigrants, demands for immediate abolition and, of course, the rights of blacks) that would endanger its success. Yet he never compromised his core belief in the wrongness of slavery. As a politician, Miller claims, Lincoln realized ''that role's fullest moral possibilities.''

Miller's conception of political leadership is informed by Max Weber's famous essay ''Politics as a Vocation,'' originally an address to students at the University of Munich during the proto-revolutionary year 1918. A believer in constitutional reform, not radical overturn, Weber insisted that the politician must be devoted to a cause yet attentive to the practical consequences of his actions. Miller insists that this ''responsible realism'' -- a combination of moral clarity and prudent responsibility -- marks Lincoln and all great political leaders.

ACCOUNTS of Lincoln always seem to require some kind of antithesis to set his greatness in sharper relief. Often this is provided by his wife, Mary Todd Lincoln, unfairly depicted as a shrew who made his life miserable. For Miller, Lincoln's foils are the era's ''utopians, perfectionists, moralizers, fanatics and absolutists,'' chief among them the abolitionists who, heedless of political consequences, demanded immediate Emancipation and equal rights for blacks.