Representative Anthony D. Weiner said on Wednesday that he could not be sure whether he was the subject in a lewd photo sent from his Twitter account that shows a man in his underpants from the waist down. But Mr. Weiner, who has been under pressure for days to answer questions about the controversy, reiterated that he had not sent the photo from his Twitter account. “This was a circumstance where someone committed a prank on the Internet,” he said in an interview with Luke Russert of MSNBC. “I didn’t send” that picture out. Mr. Weiner added, however, that he...