Douglas W. Kmiec (pronounced kah-MECK; born September 24, 1951) is an American legal scholar, author, and former U.S. ambassador.
 He is the Caruso Family Chair and Professor of Constitutional Law at Pepperdine University School of Law.
 Kmiec came to prominence during the United States presidential election, 2008 when, although a Republican, he endorsed Democrat Barack Obama.
 In July 2009, he was nominated by President Obama to serve as U.S. Ambassador to Malta.
 He was confirmed by the Senate and served for close to two years as ambassador to Malta.
 He resigned his post effective May 31, 2011.
Randall L. Tobias (born March 20, 1942) is an American governmental figure and former chief executive officer of Eli Lilly and Company.
 A Republican, he was appointed the first United States Director of Foreign Assistance, and served concurrently as the administrator of the U.S. Agency for International Development (USAID), with the rank of ambassador.
 Tobias resigned on April 27, 2007, after being linked to the D.C. Madam scandal of Deborah Jeane Palfrey.
Escort agencies are companies that provide escorts for clients, usually for sexual services.
 The agency typically arranges a meeting between one of its escorts and the client at the customer's house or hotel room (outcall), or at the escort's residence (incall).
 Some agencies also provide escorts for longer durations, who may stay with the client or travel along on a holiday or business trip.
 While the escort agency is paid a fee for this booking and dispatch service, the customer must negotiate any additional fees or arrangements directly with the escort for any other services that are not provided by the agency involved, such as providing sexual services (regardless of the legality of these services).
Robert Anthony Bradtke (born 1949) is a career U.S. foreign service officer and ambassador.
 He is the former U.S. Ambassador to Croatia and OSCE Minsk Group's US co-chair.
 President George W. Bush nominated Bradtke as U.S. Ambassador to Croatia in 2006.
 On July 7, 2006, Bradtke presented his diplomatic credentials to Croatian President Stjepan Mesić and took over in the American Embassy in Zagreb; Bradtke had previously served in Zagreb when it was part of Yugoslavia.
 In addition to Croatian, Bradtke also speaks French, German, Russian, and Italian.
Deborah Jeane Palfrey (March 18, 1956 – May 1, 2008) (dubbed the D.C. Madam by the news media) operated Pamela Martin and Associates, an escort agency in Washington, D.C. Although she maintained that the company's services were legal, she was convicted on April 15, 2008 of racketeering, using the mail for illegal purposes, and money laundering.
 Slightly over two weeks later, facing a prison sentence of five or six years, she was found hanged.
 Autopsy results and the final police investigative report concluded that her death was a "suicide".
Zalmay Mamozy Khalilzad (Pashto: زلمی خلیلزاد "Zalmay Khalīlzād"; born March 22, 1951) is a former American diplomat and a counselor at the Center for Strategic and International Studies (CSIS) and president of Gryphon Partners and Khalilzad Associates, an international business consulting firm based in Washington, D.C. He was the United States Ambassador to the United Nations under President George W. Bush.
 He has been involved with U.S. policy makers at the White House, State Department and Pentagon since the mid-1980s, and was the highest-ranking Muslim American in the Administration of U.S. President George W. Bush.
 Khalilzad's previous assignments in the Administration include U.S. Ambassador to Afghanistan and U.S. Ambassador to Iraq.
 In 2017, he was considered for U.S. Secretary of State under the Presidency of Donald Trump.
Eric Steven Edelman (born 1951) is a former Under Secretary of Defense for Policy, former U.S. Ambassador to Turkey (2003–2005), former U.S. Ambassador to the Republic of Finland (1998–2001), and former Principal Deputy Assistant to the Vice President for National Security Affairs (2001–2003).
 A career Foreign Service Officer, Edelman entered the Senior Foreign Service in 1992.
 He is a recipient of the Secretary of Defense’s award for Distinguished Civilian Service (1993) and the State Department’s Superior Honor Award (1990 and 1996).
Eric G. John (born c. 1960) is the current Senior Advisor for Security Negotiations and Agreements and the former U.S. Ambassador to the Kingdom of Thailand, having been appointed October 22, 2007.
 Ambassador John joined the Foreign Service in 1983 and has served primarily in East Asia.
 He has three tours in Korea, most recently as the Minister Counselor for Political Affairs at the U.S. Embassy in Seoul.
 He also served as the Deputy Director of Korean Affairs in Washington, D.C. His other tours include Deputy Principal Officer of the U.S. Consulate General in Ho Chi Minh City, Vietnam; the Orderly Departure Program at the U.S. Embassy in Bangkok, Thailand; and the U.S. Embassy in Dar es Salaam, Tanzania.
 In 2005, Ambassador John was named Deputy Assistant Secretary of State for Southeast Asia.
 He currently serves as the Foreign Policy Advisor to the Chief of Staff of the United States Air Force.
Gene Allan Cretz (born 1950) is a career diplomat who retired from the Senior Foreign Service in 2015.
 Before retiring, he was the U.S. Ambassador to Ghana.
 Before this, he was the first U.S. Ambassador to Libya since 1972, after being nominated in July 2007 by President Bush.
 His nomination was confirmed by the US Senate on November 21, 2008.
 He was sworn-in as U.S. Ambassador to Libya by Secretary of State Condoleezza Rice on December 17, 2008, at the State Department.
 He arrived in Libya on December 27, 2008.
 Cretz speaks a number of languages, including Arabic, Dari, Urdu, and Chinese.
 President Barack Obama nominated him for the post to Ghana in April 2012.
 He was sworn-in as the U.S. Ambassador to Ghana by Secretary of State Hillary Rodham Clinton on September 11, 2012.
 His retirement ceremony was held at the U.S. State Department on Wednesday, July 1, 2015.
Emperors Club VIP was an international escort agency based in New York City, founded in 2004 by Mark Brener and Cecil Suwal and operated from the bank accounts of QAT Consulting Group, Inc., and QAT International, Inc.
 The agency was shut down in March 2008 following a federal investigation into suspicious money transfers from New York Governor Eliot Spitzer, which led to the discovery of its operation as an illegal prostitution ring.
 Following public reports of Governor Spitzer's patronage as client #9, he resigned from office.

Question: What former U.S. ambassador resigned after being linked to an escort agency in Washington, D.C.
Answer: Randall L. Tobias