Some political scientists say that empathy is not a crucial factor in presidential races, noting that personality traits don’t correlate well with the results on Election Day. A candidate often wins despite an opponent who receives higher marks in polls asking how much each “cares about the needs and problems of people like you.”

The voters’ indifference could reflect another problem with conventional wisdom: Empathy may not be such a great quality in a leader. Although the capacity to sympathize with others’ suffering is widely hailed as an essential virtue — Mr. Obama has said the world i suffering from an “empathy deficit” — there’s a downside that has inspired a lively debate among social psychologists.

The most prominent critic is Paul Bloom, a professor of psychology at Yale, who gave a talk at this year’s meeting of the Society for Personality and Social Psychology titled “Does Empathy Make Us Immoral?” He readily acknowledges that empathy can inspire altruism — that once you “broaden your ambit of concern and empathize with the plight of others,” in Mr. Obama’s words, “it becomes harder not to act, harder not to help.”

But whom do you end up helping? Often the wrong people, Dr. Bloom says, because empathy is biased and parochial.