Anyone who knows much about the defiantly political art of Hans Haacke, filling the New Museum in New York later this month, is bound to feel anxious before meeting the famous firebrand. But when Mr. Haacke showed up for an interview at his dealer’s gallery in Manhattan, what was shocking was his quietude: In sensible sandals, roomy jeans and a staid plaid shirt, the 83-year-old New Yorker answered questions with an amiable, unflappable calm.

Asked about what seems to have been almost an embargo against him among American curators, despite his huge reputation in Europe, he replied, “before they make a move — one that is not quite the norm — they need to consider (and I don’t blame them for that) whether this is good for their personal career .”

Queried on the power of museum donors, a group he has unflinchingly confronted in his art, he replied merely that he “suspects” — and in person, Mr. Haacke never does more than “suspect”— that the power of art to affect viewers’ thinking leaves museum benefactors with “an interest in what is being shown there, and what is not going to be shown there.” And the art some donors would prefer not to see exhibited includes Mr. Haacke’s own.

“He’s just a really nice guy,” said Andrea Fraser, a peer of Mr. Haacke’s known for equally hard-nosed work. “I’ve never seen him be aggressive” — at least not in the flesh, she clarified, acknowledging the aggression in his art.