THE FORBES BUILDING IN NEW YORK City is in an odd neighborhood for a corporate headquarters: the fringe of Greenwich Village, set with sedate apartment buildings and churches from the 1840s. It's odd inside too: the ground-floor museum, founded by the late Malcolm Forbes Sr., is stuffed with presidential autographs, czarist Faberge eggs and toy soldiers. From this improbable aerie, Forbes' eldest son Malcolm ("Steve") Forbes Jr., the 48-year-old editor in chief of Forbes magazine, plans to descend into the scrum of Republican presidential politics. He could announce his candidacy as early as this week.
Shy, genial and bespectacled, Forbes looks...