Rep. Daniel Lipinski (D-Ill.), center, listens to primary opponent Marie Newman, left, at a Feb. 21 debate. Lipinski was narrowly reelected and is now one of the only antiabortion Democrats in Congress. (David Weigel/The Washington Post)

The newest class in Congress heralds a redrawing of the battle lines in the ever-contentious fight over abortion. Not so long ago, many moderate members of Congress broke from their parties over this deeply felt issue. Now, Republicans who support abortion rights are “nearly extinct.” Democrats who oppose abortion are a “dying breed.”

At the March for Life, the largest annual antiabortion event, which will take place Friday on the Mall, the increasing polarization of the antiabortion movement as an almost solely Republican issue will be in stark relief.

Leaders of the march enthusiastically welcome support from President Trump and from Vice President Pence — while insisting they want to maintain a bipartisan standpoint and a diverse crowd of attendees.

Pence spoke to marchers just days after his inauguration in 2017, and Trump addressed the march by video feed in 2018 in an address that touched on numerous Republican policy priorities, not just abortion. This year, Pence will speak at several events associated with the march, including a post-march dinner.

The march, which draws thousands of people annually, many of them youthful participants bused in from Catholic and other religious schools across the country, will also feature Democrats this year. Rep. Daniel Lipinski of Illinois, one of the only antiabortion Democrats left in the House of Representatives, will speak at the 11 a.m. rally on the Mall, along with a Democratic state legislator from Louisiana.

But some liberal-leaning antiabortion activists criticize the March for Life for alienating Democrats by embracing polarizing figures, from the president and vice president to this year’s featured speaker, Ben Shapiro, a popular conservative commentator.

“Look, when you’re streaming in video from Donald Trump and lifting up Ben Shapiro as your keynote, it doesn’t necessarily suggest that you’re too focused on broadening the tent,” said Michael Wear, a political strategist who worked for Barack Obama on outreach to religious voters and who advocates that Democrats be more open to religious views, including opposition to abortion. “Democrats generally feel marginalized at the March for Life. . . . Partisanship is trumping quite a bit these days, especially given the pretty firm stake that the establishment pro-life movement has placed in the presidency of Donald Trump.”

Wear said the March for Life could take a different tack. He pointed to the Catholic Church as an example of an institution that has never wavered from its antiabortion advocacy but has also kept at arm’s length from the Trump administration, frequently criticizing the president on other issues. Instead of Shapiro, he said, the March for Life could have invited a cardinal to speak — or an athlete or actor, all of whom the march has highlighted in the past.

He said he does not attend the March for Life. But he will speak on a panel at Evangelicals for Life, a conference that precedes the event and whose attendees typically march.

Jeanne Mancini, the president of the March for Life, said the march strives for balance, but the political climate doesn’t offer much. “We’re a bipartisan organization. And sadly, it’s gotten much, much more difficult to get Democrats to speak at the March for Life or just to be involved in the pro-life movement,” she said. “We very actively pursue pro-life Democrats.”

Definitions of who is “pro-life” and who is “pro-choice” vary, but Congress watchers have spilled barrels of ink in the past year noting that there are fewer Democrats or Republicans who disagree with their party’s majority on this issue than ever. Republicans are down to just two: Sens. Susan Collins of Maine and Lisa Murkowski of Alaska. Kristen Day, executive director of Democrats for Life for America, points out that 64 Democrats supported a 2009 amendment from Rep. Bart Stupak (D-Mich.) to Barack Obama’s signature health-care law that sharply limited abortion coverage in certain health plans, while today she counts just six Democrats she believes would qualify as antiabortion.

Voters are not as polarized as their elected representatives. Polling on Americans' attitudes on abortion is notoriously variable; a change in the wording of the question might lead to drastically different results. But reliable polls do show that attitudes toward abortion are mixed among both Republicans and Democrats. More than a third of Republican voters told Pew Research Center in 2017 that they think abortion should be legal in all or most cases, unlike their party’s leaders. And 22 percent of Democrats disagreed with their party, saying abortion should be illegal in all or most cases.

Democrats, like their leaders, seem to be moving toward greater consensus on supporting abortion rights, at least according to some polls, such as a Reuters poll in July that found a significant increase in a two-year span.

“The party has changed dramatically,” Day said, recalling the 1990s, when Bill Clinton said abortion should be “safe, legal and rare.” Democrats have taken more militant positions on the issue — including Hillary Clinton’s 2016 platform, which called for ending the 40-year-old Hyde Amendment banning federal funding for abortions — and Republicans have moved toward the opposite extreme.

“Even robustly pro-choice Democrats would be able to speak about moral reservations they had. Now that is penalized within the party by some activist groups,” Wear said. And Republicans' focus on positions like defunding Planned Parenthood have driven away non-Republican supporters of their antiabortion stances. “To be considered pro-life, you have to not only oppose abortion but also have to oppose an organization that provides contraception, provides other care to women around the country. . . . The rhetorical change has been pretty significant."

In the midst of that polarization, Mancini says that even when Trump spoke last year, she didn’t think of the march as anything close to a Trump rally.

“It’s not a political rally — what we really rally around is the human rights abuse of abortion,” she said. Citing the Democratic congressman and state legislator, plus the Republican senator and congressman who will be speaking along with Shapiro, she said, “We’ve got equal representation from both sides. That’s exciting to us.”

Shapiro said he plans to focus on science, a theme of this year’s march, and he believes he can convince open-minded listeners that life begins well before birth. “If you’re more concerned with the identity of the person making the argument than the quality of the argument, there’s not much I can do about that,” said Shapiro, who is an Orthodox Jew. “When I speak about abortion, I don’t talk in terms of religion — always in terms of logic and science.”

He said Trump’s association with the March for Life has turned away some people but that he understands why most marchers don’t mind. “The president, any time he touches an issue, it polarizes the issue,” he said. “I don’t have to endorse his personal record with regard to women, which I find egregious — I don’t have to endorse that in order to endorse the fact that he’s pro-life, especially because it’s a pro-life organization.”

Some activists involved in the March for Life say that even as the politics have become more polarized, the event has been more open to Democrats' involvement since Mancini took over in 2012 from Nellie Gray, who founded the march in 1974, a year after the Roe v. Wade decision.

But politics always creep in. “Last year, there were people within the pro-life movement, millennials, who were upset that Trump was addressing the March for Life,” said Kristan Hawkins, the president of Students for Life of America, whose college chapters flock to the march each year. She said she assured them that those of all political and religious persuasions are welcome in the movement.

“Millennials just don’t fall into the typical labels. I think the pro-life movement has to be aware of that in how we’re talking,” she said. “Do they see being pro-life as being a GOP thing? Because it’s not a GOP thing. Some of us might work with the GOP to accomplish those goals.”

She will be answering those questions again this year: Pence will be meeting with students from her group at the White House and taping a video message for the Students for Life conference associated with the march.