By a 2-1 ratio, Californians think former Democratic Gov. Edmund G. Brown Jr. would do a good, even excellent job, if he held political office today, the California Poll finds. Pollster Mervin Field said a survey of 303 adults shows 44% think Brown--out of office for five years--would be good to excellent today, and 39% rated his performance as governor equally high. But 24% felt he was a poor or very poor governor. The results are "almost the reverse of the ratings given Brown in March, 1983, two months after he left office," Field said, when 25% rated his governorship excellent or good, while 37% thought it was poor. "Part of it is just the passage of time, but part of it is a special quality Brown had and the unique way he was perceived by voters," said Field. In the last several months, Brown has mentioned several times that he intends to return to politics some time in the future.