Health care is returning as a campaign issue, with special interest and advocacy groups preparing to spend at least $60 million to push politicians to embrace universal access to medical coverage. The efforts, one by a coalition of labor and liberal groups and another by AARP, also include direct appeals to the presidential contenders and congressional candidates to change a system in which millions of people are without coverage. A coalition of labor unions and Democratic-leaning organizations called Health Care for America Now on Tuesday was announcing a $40 million campaign to promote affordable health care coverage for all. The group is spending $1.5 million on a national cable ad, and print and Web advertising. It also plans to spend $25 million on advertising through the end of the year. The effort will concentrate on key congressional districts in 45 states, where the coalition also plans to deploy 100 organizers.