But the agency’s own Office of Intelligence and Analysis, plagued by near-constant turnover at its top levels and often in turmoil, has struggled to reach its potential, insiders say. The office’s track record includes leadership battles that have fostered a toxic culture, produced intelligence that frequently is of little value and mishandled classified information that jeopardized the agency’s direct access to useful intelligence, interviews with current and former intelligence officials, court records and other documents show.