Is it possible Elizabeth Warren is becoming more bipartisan?

An earlier version of this story said that none of Elizabeth Warren’s bills had become law during the current Congress. In fact, one of her bills, to make it easier to purchase hearing aids, was incorporated into legislation reauthorizing the Food and Drug Administration that was enacted in 2017, while Congress also enacted provisions similar to bills Warren had proposed in the defense authorization law for fiscal 2018.

CONVENTIONAL WISDOM HAS IT that the Massachusetts delegation to Congress is very liberal and very partisan, with few substantive differences separating the state’s nine representatives and two senators.

Traditional methods of evaluating members of Congress—by looking at their votes—confirm this view. But in an era of party government, in which the gulf between Republicans and Democrats is as wide as ever, proponents of bipartisanship are looking for new measures to categorize narrow differences.

The Lugar Center, led by former Indiana GOP Sen. Richard Lugar, and the McCourt School of Public Policy at Georgetown University, have devised a methodology that is digging deeper. They’ve found that even as they vote in lockstep, there are important differences amongst Massachusetts’ liberals in Congress that give a better sense of their collegiality, their willingness to reach across the aisle, and their focus on policy issues.

Who would have thought, for example, that with the Republican takeover of both the Congress and the White House in 2017, Sen. Elizabeth Warren would prove more willing to work with the GOP? She wasn’t the only one: Reps. Niki Tsongas of Lowell and Jim McGovern of Worcester worked more with Republican colleagues last year than they had in the preceding Congress, when Republicans held both the House and Senate but Barack Obama was president.

Others, by contrast, were less willing to work with Republicans: Reps. Michael Capuano of Somerville, Bill Keating of Bourne and Richard Neal of Springfield. The remaining representatives and the state’s other senator, Ed Markey, have proceeded with about the same level of partisanship since Donald Trump became president as they had before—though in the case of Rep. Seth Moulton, that means maintaining his outlier standing among the delegation near the top of the bipartisan ranking among all House members.

“A lot of this just has to do with effort,” says Dan Diller, who was Lugar’s legislative director in Congress and is now policy director at the Lugar Center. “Is a member making an effort to go to the other party and try to convince them that they have a good idea?”

The Lugar Center and Georgetown evaluate congressmen by looking at the bills they’ve introduced. Lawmakers score points if their bills attract co-sponsors from the other party. They can also move up the bipartisan index if they co-sponsor bills from members of the other party.

On the plus side, the data is evaluated objectively. Lugar and Georgetown simply tally the sponsors. (The researchers don’t count ceremonial bills, such as those naming post offices, and they don’t score members who introduce and co-sponsor very few bills.)

The results add to public understanding of Congress, says Peter Ubertaccio, a political science professor at Stonehill College: “What’s happening in committees, who’s cosponsoring what—these are the sorts of things where you see gradations.”

Still, if the study has a weakness, it’s that less active legislators can look either more partisan, or more bipartisan, based on a small sample size. In 2017, Richard Neal was the least active Massachusetts lawmaker in terms of his bill sponsorships. He sponsored 11 bills and co-sponsored 95. By contrast, McGovern sponsored eight and co-sponsored 542.

Though Warren, Tsongas, and McGovern were more open to working with Republicans on bills in 2017, they weren’t high scorers in the Lugar/Georgetown study. Warren ranked as the 64th most bipartisan senator in 2017, compared to the 88th in 2015 and 2016. The study doesn’t include the Senate majority or minority leaders because they introduce and co-sponsor few bills, so the ranking is out of 98 senators instead of 100.

Both Tsongas and McGovern jumped into the top half of representatives, in terms of their willingness to work with Republicans on bills in 2017. McGovern moved up from the 281st out of 434 (the House Speaker is excluded from the ranking), to 196th; Tsongas leaped from 360th to 188th.

On the other side, Keating became the most partisan Massachusetts representative in 2017. He was the 364th most bipartisan representative last year, down from 222th in 2015 and 2016. Capuano dropped to 301st from 249th.

Both fell in the middle of the pack in terms of their legislative involvement. Keating introduced eight bills in 2017 and co-sponsored 229. Capuano introduced 21 and co-sponsored 267.

In the Senate, Markey ranked 92nd for bipartisanship in 2017 and in 2015 and 2016, having introduced 37 bills and co-sponsored another 269. Warren was slightly more active, introducing 31 bills and co-sponsoring 324.

Based on the Lugar/Georgetown data, only one Massa-chusetts lawmaker can claim real bipartisan bona fides. That’s Rep. Seth Moulton of Salem, who ranked 35th in 2017 and 34th in 2015 and 2016.

Moulton eschews introducing legislation purely to make political points. Democrats being the minority party, bills introduced by Democrats, without Republican co-sponsors, stand little chance of enactment.

Moulton only introduced five bills in 2017—to allow government workers to use Uber or Lyft on official business, to allow people suffering from Lou Gehrig’s disease easier access to government disability benefits, and to improve technology education, among others—and all had Republican co-sponsors.

The Lugar/Georgetown approach differentiates lawmakers in a way that their voting records do less and less. Congressional Quarterly, the Washington trade journal, has rated representatives and senators since 1953 on how often they side with their party on floor votes that split a majority of Republicans from Democrats.

Over the past quarter century, as southern Democrats have grown scarce and northern Republicans have become endangered, the parties have become far more unified. As a result, votes are no longer as useful in determining which members are most willing to work with those on the other side.

In the last three years, for example, the average level of party unity voting for a member of the House ranged from 94 percent for Republicans in 2015 to 96 percent for Republicans and Democrats in 2016. That’s not much of a spread.

The Massachusetts lawmaker most willing to buck his party during that time was Bill Keating, who voted with Republicans in 2015 on 6 percent of the votes that split the parties. That’s hardly a bipartisan record. Still, it passes for one when one considers that Markey and Warren sided with fellow Democrats 100 percent of the time in 2015 and 2016, and 99 percent so far in 2017.

“Votes are often tactical and often come at the end of a long, torturous process, dictated by circumstance, whipping, the mood of the day,” says Jay Branegan, a senior fellow at the Lugar Center. “Looking at bill sponsorship is more granular and considered.”

At the same time, lawmakers are regularly judged on their votes at election time, whereas bill sponsorships mostly fly under the radar. Lawmakers know that very few of the bills they put their names to will ever see the light of day. Only 97 laws were enacted in 2017, one of the lowest tallies for the first year of a Congress in modern times.

And lawmakers may have different motivations for co-sponsoring legislation. They may strongly believe in the policy and want to go on record saying so, but they also may just want to butter up a colleague or trade their sponsorship on one bill for a fellow member’s on one of theirs. Whatever the case, it does indicate a willingness to work across the aisle.

Co-sponsorships are also something lawmakers can point to at election time to demonstrate their open-mindedness, something that remains popular with many voters even as the country’s ideological divide has widened. Warren, for example, has been touting her work with Colorado Republican Cory Gardner on legislation that would require the federal government to respect state laws legalizing marijuana use. “Despite the polarization, Americans are still pretty skeptical of partisanship,” says Ubertaccio. “Candidates who can talk about their bipartisan bona fides impress voters.”

The Lugar/Georgetown data also underscore how, despite partisan differences on major legislation, much of Congress’s work is relatively uncontroversial. Warren, for example, scored points because she’s sponsored legislation with two Republicans, Charles Grassley of Iowa and Johnny Isakson of Georgia, aimed at making hearing aids more affordable and making some models available without a prescription.

She also joined forces with GOP Sen. Marco Rubio of Florida on legislation aimed at combating money laundering by human traffickers, and she’s working with Maine Republican Susan Collins on a bill to help hospitals better care for victims of terrorism.

She’s also signed on to legislation introduced by Republicans, such as a bill by Grassley that aims to expand the availability of health care in rural areas by authorizing Medicare reimbursement to pharmacists for services normally rendered by doctors. And she co-sponsored a bill by Rubio that would require the State Department to track anti-Semitic acts in Europe.

Her name on a bill hasn’t meant, for the most part, that it has a better chance of enactment. As of this spring, none of her own bills had been enacted, though her bill to make it easier to purchase hearing aids was incorporated into legislation reauthorizing the Food and Drug Administration, while provisions similar to bills introduced by Warren were added to the new defense authorization law. At the same time, six of the bills she’d co-sponsored became law, none particularly notable or controversial. The Senate passed all six, from a measure by Ohio Republican Rob Portman to bolster hearing tests for newborns and young children to one by Democrat Tammy Baldwin of Wisconsin that orders the State Department to measure how well countries are doing at compensating victims of the Nazis, without opposition.

What does it all add up to? Warren seems to be looking for more opportunities to play nice on fairly uncontroversial issues. When it comes to battles over big issues that tend to divide the two parties, look for her to revert to pugilistic form.