What happens when the nation’s foremost voice on the race question is also its most confined and restrained? Michael Eric Dyson raises this question about President Obama in his latest book, “The Black Presidency: Barack Obama and the Politics of Race in America.” The book inspires one to raise similar questions about Dyson himself. For, while hardly restrained, Dyson appears noticeably boxed in by the limitations placed on celebrity race commentators in the Age of Obama.

Readers will recognize Dyson’s practiced flair for language and metaphor as he makes an important and layered argument about American political culture and the narrowness of presidential speech. The book argues that Americans live under a black presidency — not so much because the president is black, but because Obama’s presidency remains bound by the rules and rituals of black respectability and white supremacy. Even the leader of the free world, we learn in Dyson’s book, conforms principally to white expectations. (Dyson maintained in the November issue of The New Republic that Hillary Clinton may well do more for black people than Obama did.) But Obama’s presidency is “black” in a more hopeful way, too, providing Americans with an opportunity to better realize the nation’s democratic ideals and promises. “Obama’s achievement gestures toward what the state had not allowed at the highest level before his emergence,” Dyson writes. “Equality of opportunity, fairness in democracy and justice in society.”

A certain optimism ebbs and flows in “The Black Presidency,” but only occasionally does it refer to white Americans’ beliefs about race. Far more often, Dyson hangs hope on Obama’s impromptu shows of racial solidarity. One such moment was the president’s remarks after the 2009 arrest of the Harvard professor Henry Louis Gates Jr. (who was arrested trying to get into his own home). Another was Obama’s public identification with Trayvon Martin. Both acts may have been politically risky, but they also greatly heartened African- Americans. Hope builds, and by book’s end, readers find a chapter-long celebration of the president’s soaring invocations of “Amazing Grace” during last year’s memorial service for the slain parishioners of Emanuel A.M.E. Church. For Dyson, the eulogy at Emanuel seems to serve as a sign of grace that black America may still yet enjoy from the Obama White House.

Its cresting invocations of hope aside, the book ably maintains a sharp critical edge. Dyson uncovers a troubling consistency to the president’s race speech and shows that in spite of Obama’s reliance on black political networks and black votes during his meteoric rise, the president chose to follow a governing and rhetorical template largely hewed by his white predecessors. As both candidate and president, Obama’s speeches have tended to allay white guilt. They have scolded ­African-American masses for cultural pathology and implied that blacks were to blame for lingering white antipathy. Obama’s speeches have also often consigned the worst forms of racism and anti-black violence to the past or to the fringes of American political culture. One finds passive-voice constructions everywhere in Obama’s race talk, as black folk are found suffering under pressures and at the hands of parties that go largely unnamed. “Obama is forced to exaggerate black responsibility,” Dyson advances, “because he must always underplay white responsibility.”