There’s an old Egyptian joke that took on special resonance during the Arab Spring, when then-President Hosni Mubarak finally appointed a vice president after nearly three decades in office. “When [Gamal Abdel] Nasser became president, he wanted a vice president who was dumber than he was, so as not to cause him trouble or pose a threat to his power, so he chose [Anwar] Sadat. When Sadat became president, he, too, wanted a vice president dumber than he was and picked Mubarak. Mubarak waited three decades to pick a vice president because he, too, was waiting to find in Egypt someone dumber than himself…”

It’s a joke that encapsulates much of the common wisdom of vice presidents. First, the most important thing about vice presidents (despite the modest growth in their influence in the U.S.) is that they may suddenly become president. Second, it is a reminder that presidents select vice presidents who won’t be a threat. The second point undermines the first; it is little surprise that most vice presidents flounder when the spotlight turns to them.

There’s an old Egyptian joke that took on special resonance during the Arab Spring, when then-President Hosni Mubarak finally appointed a vice president after nearly three decades in office. “When [Gamal Abdel] Nasser became president, he wanted a vice president who was dumber than he was, so as not to cause him trouble or pose a threat to his power, so he chose [Anwar] Sadat. When Sadat became president, he, too, wanted a vice president dumber than he was and picked Mubarak. Mubarak waited three decades to pick a vice president because he, too, was waiting to find in Egypt someone dumber than himself…”

It’s a joke that encapsulates much of the common wisdom of vice presidents. First, the most important thing about vice presidents (despite the modest growth in their influence in the U.S.) is that they may suddenly become president. Second, it is a reminder that presidents select vice presidents who won’t be a threat. The second point undermines the first; it is little surprise that most vice presidents flounder when the spotlight turns to them.

The U.S. raid seizing Venezuelan President Nicolás Maduro has put Venezuelan Vice President Delcy Rodríguez front and center on the global stage. Under the Venezuelan Constitution (written under former President Hugo Chávez), the vice president is more akin to a prime minister. It is a powerful, not ceremonial, position in the state apparatus. Maduro selected her because she was a loyal Chavista, but she has high-level political experience and a strong political base of her own in connection with her brother, Jorge.

That means she may be better positioned than most to take advantage of the opportunity suddenly offered to her. But the record of her vice presidential peers suggests disappointment. There are modest reasons that Rodríguez might buck the odds, but it is not an encouraging pattern.

Here in the United States, vice presidents have ascended to the presidency and met the moment (Harry Truman), been political ciphers (Millard Fillmore), or been disasters (Andrew Johnson). But across the world, the pattern has been one of failure—and sometimes bringing regimes down with them.

Egypt’s own record contains both surprising success and stagnant failure. When Sadat ascended to the presidency after the death of the charismatic pan-Arabist icon Nasser in 1970, Sadat was seen as a lightweight who would be easily managed by the Nasserists.

But Sadat purged the Nasserists from the government—imprisoning the vice president, the minister of war, and the hated minister of the interior, who controlled the pervasive mukhabarat (secret police). Egyptian Nobel laureate Naguib Mahfouz said that under Nasser, “I always worried that one night someone would come knocking at the door.”

Sadat began to open Egyptian society economically and politically. He distanced Egypt from the Russians while reaching out to the United States. The initial successes of the Arab-Israeli War in 1973 gave Egypt a psychological victory after the humiliating defeat of 1967. With this political capital, Sadat was able to break with the other Arab leaders and make his dramatic 1977 trip to Jerusalem in which he spoke to Israel’s Knesset and pledged his readiness to make peace.

Sadat did not solve the myriad problems facing Egypt. Some he made worse, such as empowering Islamists against the communists. But ending a costly and fruitless conflict was a worthy achievement—and one for which he paid the ultimate price. He was assassinated in 1981. It was a terrifying moment not only in Cairo but around the world. It could have been a harbinger of an Islamist revolution, as had recently occurred in Iran, or the end of Egypt’s peace treaty with Israel.

Egypt’s vice president, a career Air Force officer, Mubarak, assumed office. He promised to be a steady hand, keeping the treaty with Israel and maintaining Egypt’s secular pro-Western government. Mubarak made no bold moves. He preferred to muddle through, leveraging Egypt’s geopolitical importance for U.S. support, cracking down on Islamic terrorists, while allowing radical Islamists to spread throughout Egyptian society. The economy stagnated, utterly unable to keep pace with Egypt’s burgeoning population. Political reforms proved illusory. The mukhabarat became even more omnipresent and brutal. Efforts at economic liberalization only enriched Mubarak’s cronies.

Mubarak’s ploy succeeded for nearly three decades, until he was forced from power in February 2011 during the Arab Spring. (Only a month before, he had finally appointed his own vice president.)

The Egyptian experience is not encouraging—but when truly inept vice presidents ascend, as in Argentina or the Soviet Union, they can bring down the entire regime.

When Argentina’s Juan Perón died in July 1974, his third wife, Isabel, was vice president. A former nightclub dancer, Isabel Perón lacked the savvy or appeal of Perón’s late second wife, the legendary Evita. Beset with political violence along with its perennial economic crisis, Argentina rallied behind its new president—but the honeymoon didn’t last.

The éminence gris of her presidency was the minister of social welfare, José López Rega, a corrupt former police officer who established an anti-communist paramilitary force, shared Isabel Perón’s obsession with the occult, and forced out competent ministers who could threaten his position. The military overthrew Isabel Perón on March 23, 1976, and proceeded to engage in mass terror and ultimately a disastrous war that brought their regime to an end.

In 1991, Kremlin hard-liners decided that Soviet President Mikhail Gorbachev’s reforms had gone too far. The plot to remove Gorbachev was led, unsurprisingly, by the KGB chief. But formal authority would go to Vice President Gennady Yanayev, who was co-opted by the coup plotters.

The Soviet Union had only just created the vice presidency. Gorbachev chose Yanayev, a nonentity who had only just reached the Politburo. Yanayev was a Communist Party loyalist and was probably appointed as a sop to the opponents of reform, but he would be no threat. David Remnick, in Lenin’s Tomb: The Last Days of the Soviet Empire, wrote that Yanayev: “…was the worst sort of Party nonentity. He was a vain man of small intelligence, a womanizer, and a drunk. I’m not sure it is possible to describe just how hard it is to acquire a reputation as a drunk in Russia.”

On Aug. 18, 1991, with Gorbachev on vacation, the coup began by cutting the communications to Gorbachev’s dacha. In the small hours of Aug. 19 Yanayev signed papers initiating the State Committee for the State of Emergency. In the late afternoon, Yanayev held a press conference in which his hands visibly shook and his voice trembled. He had already been drunk when he signed the papers early that morning, and he continued to drink throughout the day.

Days later, when the coup collapsed, the Soviet Union collapsed with it. Yanayev’s “presidency” lasted for a whole three days; after a brief prison term and pardon he went to work for the national tourism agency.

Rodríguez is no Yanayev or Isabel Perón—although regime collapse cannot be discounted. Maduro himself became president when the founder of the Bolivarian regime, Chávez, died in 2013. Lacking the charisma of Chávez and in the face of declining oil revenues, Maduro held on to power through brutal repression, rigging elections, and balancing factions within the regime. Just like Mubarak, Maduro muddled. But Rodríguez may be a different sort of political animal. Throughout her vice presidency, Rodríguez has shown initiative, crossing ideological barriers to reach out to business communities and potentially to the United States.

Will Rodríguez meet the moment, or will she do the Mubarak/Maduro muddle? For American policymakers, the question is whether Rodríguez can be encouraged to undertake real reform, or if instead transactional arrangements will allow the stagnant Bolivarian regime to continue under new management.