It used to be called “the Jesse Jackson problem”: Democratic presidential candidates fearing they would lose black votes if they got on Mr. Jackson’s bad side, given the influence he accrued as a civil rights activist and his history-making races for the White House in 1984 and 1988.

But if his recent critical comments about Senator Barack Obama prove anything, Democrats and political scientists said Thursday, it is that a Jesse problem these days can actually help a candidate like Mr. Obama  with white voters who have questions about whether Mr. Obama shares their values, and with black voters who see Mr. Jackson as a figure of the past.

Even Mr. Jackson’s 43-year-old son, Representative Jesse Jackson Jr. of Illinois, went beyond repudiation to excoriate him  a poignant reminder that a real generational shift in power and leadership is under way in African-American politics. Mr. Obama, 46, has already overshadowed former President Bill Clinton, once a deeply popular figure among black Americans; if anything, Mr. Obama seems likely to gain political dividends from Mr. Jackson’s vulgar criticism of him for, as Mr. Jackson put it, “talking down to black people” in speeches about the responsibilities of absent black fathers.

“This moment only reinforces that we have to let the younger guys take the lead in politics, that they know the issues of today, that we live in a far different world than 20 years ago,” said Michael S. Dukakis, the Democratic presidential nominee in 1988, when Mr. Jackson won a series of nominating contests, including those in Georgia, Michigan and Virginia.