Jarrett’s official job description is “somewhat vague,” Becker writes, noting that at least part of her role is to serve as “chief liaison to the business community, state and local governments, and the professional left,” but her influence is undeniable. She commands a staff of nearly three dozen and has a hand in decisions ranging from the invitation list to state dinners and what gifts to give foreign leaders, to who should be nominated to the Supreme Court, appointed to a vacant ambassadorship, or awarded the President Medal of Freedom. When Warren Buffett visits to the White House for lunch, the table is set for three.

White House memos are littered with references to what “VJ thinks” or “VJ says.” When Standard & Poor’s downgraded the country’s credit rating in August 2011, she was among a select few invited to Camp David to discuss how to manage the fallout. She is “effectively the chief of staff,” in the words of one White House adviser, which likely explains her problematic relationships with actual chiefs of staff such as Emanuel and his successor Bill Daley, who did not appreciate the fact that Jarrett went behind his back (and Vice President Joe Biden’s) to help orchestrate the administration’s controversial contraception mandate, along with her “good friend,” Health and Human Services Secretary Kathleen Sebelius.

Tellingly, despite presiding over one of the greatest political disasters in recent memory, Sebelius remains at her post, whereas Jarrett’s enemies rarely stick around for long. The White House reportedly went to great lengths last month to out a senior official — Jofi Joseph of the National Security Council — who had been operating an anonymous Twitter account, @natsecwonk, which was highly critical of the administration. Among Joseph’s offending tweets: “I’m a fan of Obama, but his continuing reliance and dependence upon a vacuous cipher like Valerie Jarrett concerns me.” Joseph was fired immediately after his identity was discovered in a sting operation coordinated by the White House and State Department.