After the disaster of the 1968 Democratic National Convention in Chicago, a security committee of key convention officers, city officials, and law enforcement representatives has functioned at subsequent conventions. It is responsible for security inside the convention, while local police are responsible for the exterior. The committee monitors the credentials operation, floor access, and security for social events. The police focus on demonstrators and scheduling them to prevent conflicts. Security concerns have changed conventions, becoming the largest single expenditure in convention budgets and influencing site selection. The Secret Service is responsible for protecting candidates at the Democratic and Republican conventions, although it must coordinate with other security forces regarding traffic control and perimeter protection. Press coverage, both in terms of people and equipment, presents additional problems, although networks usually supply their own security people. Most planning for the Republican convention has been spearheaded by the Dallas Police, who researched planning documents from previous conventions and visited former host sites. One problem for Dallas is maintaining services for the city with about 55 percent of the police department committed to the convention.