Richardson, who has long supported improved relations with Cuba, said he was “flabbergasted” by his treatment. He was invited to Havana by the Cuban government to discuss the Gross case, he said, leading to hopes of a breakthrough. Cuban parliament leader Ricardo Alarcon last week described Richardson’s trip as “noble.”

But Richardson said there appeared to be disagreements within the Cuban government on what to do with Gross.

“My sense is, there are some elements in their government that don’t want to improve relations with the U.S.,” Richardson said.

According to the Washington Post, Richardson traveled to Cuba with the blessing of the State department, which briefed him before his departure. But the rebuff does somewhat call into question the notion of high-profile ex-politicians being sent to secure the release of hostages or win concessions from foreign regimes.

He's a quick look at the success rate of some of America's most prominent freelance troubleshooters:

Bill Richardson:

Successes: The veteran negotiator has a long list of successful interventions, including being the first nonfamily member to visit Burmese opposition leader Aung San Suu Kyi, negotiating the release of U.S. oil workers being held by Saddam Hussein's government in 1995, and negotiating the release of three Red Cross workers being held by Sudanese rebels in 1996.

Failures: Richardson met secretly with then Yugoslav leader Slobodan Milosevic in 1996, and brought home a proposed Balkan peace plan which was immediately rejected by the Clinton administration. Richardson also negotiated a ceasefire in 2007 between Sudanese President Omar al-Bashir and rebel forces in Sudan, which was violated just a few weeks later.

Jimmy Carter

Successes: Former President Carter has gone on diplomatic missions under each of his successors, including peace missions to Ethiopia, Sudan, North Korea, Haiti, and the former Yugoslavia. His denunciation of the rigged 1989 election of Manuel Noriega in Panama was called a "masterpiece of guerilla diplomacy" by the New Republic. With Bill Clinton's blessing, Carter helped broker a groundbreaking nuclear deal with Kim Il Sung's North Korea in 1994 -- though that hasn't stood up so well to the test of time.

Failures: In more recent missions, Carter has seemed strangely credulous in playing messenger for the autocratic regimes with which he negotiates. After a trip to North Korea last year to secure the release of U.S. hostage Aijalon Gomes, Carter penned an op-ed in the New York Times arguing that Pyongyang is sincere in its desire to restart the six-party talks, though it has walked away from table numerous times over the past decade. Along with his fellow "elders," Carter traveled to North Korea again this year, arguing against prejudging the regime's intentions and blaming international sanctions for poor humanitarian conditions in the country.

Jesse Jackson

Successes: The civil rights activist and former presidential candidate's forays into international diplomacy have usually been conducted without the approval -- and sometimes with the active opposition -- of the U.S. administrations in power. Nonetheless, to give credit where it's due, Jackson has demonstrated a knack for securing the release of U.S. hostages, successfully negotiating with dictators including Milosevic, Saddam, Castro, and Hafez al-Assad. It's quite possible that these leaders were willing to make a deal with Jackson because his efforts were so unpopular with the U.S. governments of the time.

Failures: Jackson's one experience as an actual accredited diplomat didn't go so well. In 1997, Bill Clinton appointed him as a special envoy for promoting democracy in Africa, despite his having no previous experience in African affairs. Jackson made a particularly ham-handed attempt to negotiate a peace deal in Sierra Leon on a 2000 trip, during which he compared the brutal Charles Taylor-backed warlord Foday Sankoh to Nelson Mandela. More than 50,000 would be killed in the war between the government and the rebels led by Sankoh, who died while awaiting trial for crimes against humanity.

Bill Clinton

Successes: According to reporting by FP's Josh Rogin, a long list of VIPs were anxious to go on a mission to North Korea to secure the release of U.S. journalists Laura Ling and Euna Lee, including Richardson and Sen. John Kerry. Al Gore, who owns network the two journalists work for, was reportedly considered but then rejected by the North Koreans, who insisted on former President Clinton. Clinton traveled to North Korea, sat for one of the most awkward photo-ops of all time with Kim Jong Il, and brough the two home.

Failures: So far, Clinton's batting .100. But he's a relatively new addition to the club of former Democratic politicians-turned-freelance diplomats so we'll have to see.

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And of course, who could forget former Washington D.C. Representative Walter Fauntroy's recent eventful jaunt to Libya, during which he was briefly trapped at the Rixos Hotel, claimed to have seen European special forces troops beheading rebel fighters in order to demostrate their control, and called the international intervention the first step of the European recolonization of Africa. Something tells me he won't be on the White House's shortlist the next time hostages need rescuing.