WASHINGTON -- When President Barack Obama and GOP rival Mitt Romney square off Monday for a foreign policy debate, the question of whether sanctions on Iran have worked is sure to be one topic. But the question really is a larger one: Do sanctions work? And the answer depends on how the objective is defined.

Romney criticizes Obama for a sanctions-driven approach to thwarting Iran’s pursuit of nuclear weapons. Yet his own fix is partly to toughen sanctions that target Iran’s central bank. Neither candidate has said they’re willing to use the American military against Iran, so sanctions that harm Iran’s economy are the preferred approach.

The overall success rate for sanctions seems questionable. There’s been a U.S. economic embargo on Cuba now for more than five decades, and the Castro brothers remain in power. A decade of sanctions against Saddam Hussein failed to topple him; he didn’t go until the United States invaded Iraq. There’ve been U.S. sanctions on Iran since the days of Jimmy Carter and the hostage crisis, yet Iran continues developing a nuclear program.

“Sanctions play a direct role and an indirect role in a policy like our Iran policy,” explained Michael Singh, managing director of the Washington Institute for Near East Policy, a security think tank.

The direct role is to inflict pain, imposing a cost on the activity you wish to stop. The indirect role, he said, is to hit the wallet of the elites in Iran, people who hold sway with policymakers there.

“That said, sanctions (alone) have a pretty poor record in themselves in accomplishing policy goals,” said Singh, who was the senior director for Middle East affairs in the George W. Bush administration’s National Security Council.

The public often measures the success of sanctions by whether an autocratic regime is toppled from power. Sanctions are a means to that end, but they’re usually deployed as part of a broader strategy.

“Sanctions are an economic tool. The economic dimension of sanctions can have an impact,” said David Gordon, the State Department’s policy planning director from 2007 to early 2009 and now director of research for the Eurasia Group, a political risk analysis firm. “The ‘working’ is always a political question, because sanctions with very, very few exceptions have explicit goals.”

Iran sanctions seek to pressure that nation to comply with U.N. inspections, disclose the full history of its nuclear program and halt enrichment of uranium. Sanctions against Serbia in the 1990s helped achieve negotiations that led to the Dayton peace accords, ending the Bosnian war. Sanctions against South Africa helped pressure the white-ruled government to negotiate an end to apartheid.

“I think that the record of sanctions . . . is mixed. I think the use of sanctions in Iran made a lot of sense,” Gordon said. “Have they worked fully? No. Have they changed the game, and are they changing the game? Yeah. Their end impact remains uncertain.”

The Obama administration has sanctioned Iranian ship lines, insurance companies, banks, a range of industries and sectors. The Iranian currency has lost 40 percent of its value and ordinary Iranians feel the pain of economic isolation.

The real success, however, has been in Russia and China both backing U.N. sanctions on Iran, and Europe matching and at times exceeding U.S. sanctions.