WITH THE presidential election over, supporters of better U.S.-Cuban relations are calling on President Obama, who won a majority of the Cuban American vote, to seek accord with the Castro regime. They forget the case of Alan Gross, the American development contractor who this week began his fourth year in a Cuban military prison.

Mr. Gross, of Potomac, was arrested on Dec. 3, 2009, after he delivered satellite telephones to members of Cuba’s tiny Jewish community. He had been hired to provide the equipment by the U.S. Agency for International Development; the aim was to help Cuban Jews connect to the Internet.

In 2011, Mr. Gross was convicted of crimes against the state and sentenced to 15 years in prison. There the now-63-year-old has remained, despite health problems that include a severe loss of weight, arthritis and a growth on his shoulder. His appeals to visit his gravely ill, 90-year-old mother have been denied. Cuban president Raúl Castro has repeatedly turned down proposals to release Mr. Gross on humanitarian grounds, despite visits from envoys ranging from U.S. senators to former U.N. ambassador Bill Richardson.

The Castro government says it wants to repair relations with the United States, win the lifting of what remains of the U.S. trade embargo and attract investment from American companies. So why keep Mr. Gross in prison? The answer, unfortunately, is relatively simple. Cuba wants to swap its prisoner for five Cuban spies who were arrested in Florida in 1998. The network infiltrated a U.S. Navy base and anti-Castro groups and provided information that facilitated Cuba’s 1996 shoot-down in international airspace of two planes carrying members of one of the groups. Four U.S. citizens died. The head of the network was sentenced to life in prison after a 2001 trial, while others were given lesser terms. One is now out on probation.

There is no equivalence between Mr. Gross and the five prisoners, as Havana itself acknowledges. It agrees the Florida prisoners were its spies, but it has never charged Mr. Gross with espionage. But Mr. Castro sees Mr. Gross as the leverage to spring his agents, whom the state propaganda apparatus portrays as heroes. More significantly, by arranging an exchange, the regime believes it can reshape U.S.-Cuban relations on its own terms, without having to make concessions on human rights.

The Gross family has appealed to Mr. Obama to send a high-level envoy to Cuba and to do what is necessary to obtain his release. That’s understandable, but the administration ought to stick to its refusal to countenance such a bargain. On the contrary, Mr. Obama should consider new steps to punish the Castro regime for the continued imprisonment of Mr. Gross, and the administration should do more to raise his case in international forums.

Better relations between Cuba and the United States must be conditioned on real steps toward democratization by Havana. But until Mr. Gross is released, they ought to get worse.