The most popular song in America--for this week, anyway--is Stevie Wonder's "Part-Time Lover," which is now in its fourth straight week at No. 1 on the black charts and in its second week in the top spot on the adult contemporary list.

But "Part-Time Lover" is unlikely to have quite the chart run that "I Just Called" enjoyed, because there is yet another hot challenger ready to take over as America's No. 1 single--Jan Hammer's "Miami Vice Theme," which jumped from No. 4 to No. 2 this week and looks like a sure-fire No. 1.