What cosponsorships tell us about Beacon Hill in 2025
One of the biggest questions in all of politics, at every level, is who is close with whom.
If you’re an advocate, lobbyist, reporter, or an elected official, knowing the webs of influence in a political body is critical if you’re to advance your agenda. Unfortunately, there is no book where every legislator writes what they think of everyone else that we can read. That is left to guesses, deductions, and gossip.
There is, however, one place when legislators do publicly declare when they agree with each other on specific issues - sponsoring legislation.
Mapping our relationships on Beacon Hill
Network analysis is the study of social relations among a set of people by means of graph theory. It has been used to look at everything from Congress to the Seven Kingdoms and can uncover aspects of an institution that would otherwise be too difficult to parse out. We did this for Massachusetts in 2021 and are checking back in with the new data provided by the cosponsorships for the session that began in 2025.
You can jump to the data to see the full stats and read more for some takeaways.
How we slice the data
We collected the sponsors and co-sponsors of all bills on the State House’s website as of February 19, 2025. Each time two legislators were on the same legislation, that was treated as a connection between them. We then weighted the connections proportional to how many sponsors the legislation had. A bill with two sponsors was a connection of 0.50 between them. A bill with ten sponsors meant a connection worth 0.10 between all of them. And so on.
We then took this map of connections between legislators and used three measurements to derive some insights:
Centrality: the legislators that appear in the middle of this network closest to others.
Closest pairings: who each legislator co-sponsored the most with.
Communities: an algorithm estimated what it thought were groupings of legislators, those who seem to cosponsor more with each other than they would randomly.
How you can use the data
If you’re looking to better understand Beacon Hill and move your policies, here are some ways to look at this data. We want to stress, it’s only one perspective from one dataset, to be supplemented by your own analysis and what you hear.
All else being equal, more central legislators are probably more effective internal advocates for your issue. Obviously, leadership positions and committee membership is hugely important, but you may also want to get your material in front of those who seem to have closer shared interests in the building, if only to market their support.
If you’re looking to connect with a legislator, look at who are their highest cosponsor pairings. If you have only a few legislative champions, this could also provide a map to a committee chair you need. Look at who that chair cosponsors with, then who those people cosponsor with, and so on until you reach someone who supports your bill.
While these communities are drawn by algorithms and not an analyst, it might be helpful to start by talking with members of different communities in case that throws up unexpected differences in questions.
What the data tells us
Cosponsorships on Beacon Hill indicate a few things, in no particular order:
Centrality in the network does not seem to be dependent on how many bills someone sponsors or their longevity. The top ten include those who sponsored as few as 16 bills and as many as 186, and includes Democrats, Republicans, someone first elected in 1990 and someone elected last year. Rep. Rich Haggerty was the most central legislator overall.
Republicans tend to sign onto each others’ bills. Brad Jones, Paul Frost, Kimberley Ferguson, and Hannah Kane have the highest cosponsorship pairings between them, with Sens. Joanne Comerford and Jamie Eldridge the most-cosponsorsing Democratic pair.
Legislation is often proposed in a bipartisan way on Beacon Hill. Although there is one algorithmically-detected community that is the most Republican, there are Democrats in that one, and even a Republican in a community that includes a large number of the Progressive Caucus.
How Legislata can help
If you’re looking to follow what’s happening on Beacon Hill, Legislata is making AI-generated transcripts for all House and Senate sessions and committees available for free on our app. You can see them here, and you can also sign up for a free account to be alerted when a new transcript is posted or a specific keyword of your choice is mentioned.