ACCORDING TO A REPORT published by Pew Research in October 2017, the divide between Republicans and Democrats is the widest it’s been in the last 23 years, reflecting a sharp rise in political partisanship that threatens our ability to solve some of the nation’s most pressing problems.

That’s why US Rep. Niki Tsongas’ accomplishments over the past 11 years were remarkable.

Tsongas worked effectively as a Democrat in a Republican-controlled House — passing laws and delivering millions in federal dollars to her district — not by chasing headlines or resorting to inflammatory language and partisan rhetoric, but by listening, seeking to understand opposing viewpoints, and finding opportunities for common ground. She framed her language and her approach in terms of cooperation and progress, focusing on what she was fighting for rather than who she was fighting against.

Alongside US Rep. Mike Turner, a Republican from Ohio, she made historic strides to combat sexual assault in the military, increasing support for victims seeking justice and creating a safer, more inclusive culture for women serving our country. When the two visited UMass Lowell together in 2014 for a defense sector roundtable — fresh off a visit to Wright-Patterson Air Force Base in the heart of Rep. Turner’s district — I was immediately struck by the mutual respect they had developed on the House Armed Services Committee, despite their political differences.

I know from my own 14 years in Congress how difficult it can be to forge those kinds of relationships. Both parties put enormous pressure on their members to push a partisan agenda. When I worked with US Rep. Chris Shays, a Republican from Connecticut, on a bill that would eventually become the Bipartisan Campaign Reform Act of 2002, both of our parties strongly resisted our efforts and attempted to drive a wedge between us.

More than 15 years later, the rift between Democrats and Republicans has become a chasm, forced ever wider by the extreme right and left that were once the fringe and are now the base of each party. In that environment, many in Congress have thrown their hands up, bemoaning obstructionists across the aisle, and pointing fingers at the opposing party as responsible for the gridlock in Washington.

In contrast, Niki Tsongas continued to practice the dying art of bipartisanship while still remaining true to her progressive principles. She advocated tirelessly for LGBTQ rights as a founding member of the Congressional Equality Caucus for Lesbian, Gay, Bisexual and Transgender Americans, choosing to inform rather than chastise those who opposed her efforts.

When I worked as a press assistant to US Rep. Jim Shannon nearly 40 years ago, it was common for House Speaker Tip O’Neill to play golf with House Republican Leader Bob Michel on the weekends or meet with President Ronald Reagan for drinks at the White House. It was a time when politicians could disagree without demonizing each other, when they could find a way to build relationships and work together despite their differences.

Washington’s male-dominated culture, writ large, has come a long way since that time, due largely to the number of women now running for and winning office. Tsongas herself was the first woman elected to Congress from Massachusetts in 25 years, and as of this week, our delegation now boasts four women, including our first African American congresswoman. As a result of the mid-term election, Congress as a whole looks much more like the nation it represents, which is a victory for democracy. But that progress and its promise of change is hindered by the extreme partisanship that has become the norm in Washington.

As a member of Congress, Niki Tsongas fundamentally understood that when political parties focus only on defeating each other, we all lose.

Both the new and returning members of the Congress she recently departed should look to her example.

Martin T. Meehan is president of the University of Massachusetts. He served in the US House of Representatives from 1993 to 2007, representing Massachusetts’ 5th congressional district.