After weeks of Cabinet speculation revolving around the same old names, the last few days have added a few new ones, among them James G. Watt, now considered the front-runner for interior secretary.

Watt is an attorney who specializes in fighting excessive governmental regulation -- just the ticket for the antiregulation Reagan forces. The 42-year-old Watt, president of the Mountain States Legal Defense Foundation in Denver, also meets Reagan's reported criterion that the interior secretary be from a western state. And he has the stamp of approval of a number of western legislators, not to mention the support of Joseph Coors, Colorado beer mogul, who is a Reagan adviser and a longtime supporter of conservative causes.

He has Washington experience and Interior Department experience, having served as a congressional aide, as a deputy assitant interior secretary and as a member of the Federal Energy Regulatory Commission before moving to Denver.

He seems to have qualifications to please everyone, in fact, except possibly the environmentalists. While Watt himself says he favors a "balance" between those who would develop natural resources and those who would preseve them, he has spent his time at the Mountain States foundation pressing lawsuits to stop regulation of Colorado air pollution and to speed oil and gas leasing in Wyoming.