ORLANDO, Fla. — The Interstate 4 corridor stretching from the Tampa Bay area through Orlando to Daytona Beach is a bellwether of the nation’s largest swing state, where both candidates campaigned vigorously last week and President Barack Obama on Friday called on voters here to support Hillary Clinton.

North Florida is predictably Republican, and South Florida remains strongly Democratic, leaving a swath around Interstate 4 as the state’s primary battleground.

The 6.5 million residents living around the 140-mile highway reflect the diversity of the state, and they account for a third of Florida’s registered voters. The large bustling metros of Tampa and Orlando are broken up by the citrus and cattle fiefdoms of Polk County.

Kissimmee in suburban Orlando has become a destination for Puerto Ricans fleeing the deteriorating economy on the island. The suburbs of Orlando give way to the motors sports traditions of Daytona Beach and the gateway to the Kennedy Space Center.

More than a third of I-4 voters are registered Democrats, a third are registered Republicans and a quarter have no party affiliation.