There are a large number of newspaper databases available to Northeastern students that can be searched for articles supporting clemency. Go to Northeastern Databases A-Z and use the dropdown under Type to choose news and newspapers.
The Boston Globe, Current and Historical (1872-present) (Proquest) can help you find articles supporting clemency in Massachusetts, but there are other state newspapers available as well. Take a look at the states that grant clemency the most frequently and try searching the local paper for articles of support.
Here's an example of a recent news article from the Boston Globe:
A few more general secondary sources on clemency:
Petitions and initiatives to amend the Massachusetts Constitution are governed by Art XLVII. The State Law Library has provided a good overview of the initiative petition process and the legislative amendment avenue.