Political change was under way. The UCD was a coalition that encompassed a wide range of frequently incompatible political aspirations. Internal conflict had been muted in the interest of maintaining party unity in order to protect the transition to democracy. When the 1979 elections appeared to affirm this transition, the centrifugal tendencies broke loose. In the succeeding months, the center-right UCD moved farther to the right, and its more conservative members were increasingly critical of Suarez's compromises with the PSOE opposition on political and economic issues. At the same time, large segments of the population were frustrated that Suarez did not produce a more thorough reform program to eliminate the vestiges of authoritarian institutions and practices.

Suarez's failure to deal decisively with the regional problem further eroded his popularity. Repressive police measures met increasingly virulent outbreaks of Basque terrorism, and the ongoing spiral of repression and terror contributed to a growing impression that the government was incompetent. The mounting violence further exacerbated Suarez's relations with the military, which were already strained because of his legalization of the PCE. Army leaders, who had only grudgingly accepted political reforms out of loyalty to Juan Carlos, grew increasingly hostile to the democratic regime as ETA terrorism intensified. A coup plot had been uncovered in the fall of 1978, and the possibility of military subversion continued to be a threat.

As discontent with his leadership grew, Suarez realized that he had lost his effectiveness, and on January 29, 1981, he announced his resignation as prime minister. The king appointed conservative centrist Leopoldo Calvo Sotelo to replace him. Before the new prime minister could be confirmed, a group of Civil Guards, led by Lieutenant Colonel Antonio Tejero Molina, marched onto the floor of the Cortes and held the representatives hostage in an attempted coup. The plan of the rebellious military leaders was to set up an authoritarian monarchy under the protection of the armed forces. That the coup failed was primarily due to the decisive action of Juan Carlos, who ordered the conspirators to desist and persuaded other military officers to back him in defending the Constitution. Juan Carlos then appeared on television and reassured the Spanish people of his commitment to democracy. The foiled coup was over by the next day, but it demonstrated the fragility of Spain's democracy and the importance of Juan Carlos to its continued survival. On February 27, more than 3 million people demonstrated in favor of democracy in the capital and elsewhere throughout Spain, showing the extent of popular support for democratic government.

Data as of December 1988