Democrats with conservative positions on social issues such as abortion continue to disappear from Congress. Half as many pro-life Democrats sit in Congress today than two years ago, and—thanks to redistricting and retirements—in six months the number may be cut in half again.

Of the 20 Democrats who voted for a May bill that would ban gender-based abortions, as few as eight are likely to win reelection. And the number is almost certain to be no higher than 13.

In the 2010 election, pro-life groups targeted pro-life Democrats who supported President Obama's health-care law. Even some Democrats who opposed the law faced opposition by conservatives who saw the midterm election as a golden opportunity to put a more conservative Republican in office. The result: The number of pro-life Democrats shrank by half.

This time around, Democrats are less vulnerable on the abortion issue, but many face new districts with lines redrawn after the latest census.

In Pennsylvania, a reduction in the number of House seats resulted in two Democrats with pro-life records facing off in April. Jason Altmire (PA-4) lost to Mark Critz (PA-12) in a rare incumbent-versus-incumbent primary.

Two days before voting for the gender abortion bill, Silvestre Reyes (TX-16) lost a reelection bid to Beto O’Rourke, who drew attention for his support of legalizing marijuana. He had served in the House since 1997 and had even won a rare primary election endorsement from President Barack Obama.

Heath Shuler (NC-11) barely held his seat in 2010; this year he faced an even more difficult race after district lines in North Carolina were redrawn, so he decided to retire. Mike McIntyre (NC-7) is staying in his race, but many analysts consider it a toss-up.

"As the Democratic and Republican parties have taken opposite sides on abortion, so have Democrats and Republicans in the public," said John Sides, a political scientist at George Washington University. "People's views on abortion are increasingly aligned with their party's."

Other pro-life Democrats are retiring rather than seeking reelection. Jerry Costello (IL-12), Joe Donnelly (IN-2), Mike Ross (AK-4), and Dan Boren (OK-2) each will retire at the end of this term. The number of pro-life senators will shrink further this fall when Sen. Ben Nelson (D-Neb.) retires since the state is expected to elect a Republican.

Only a few pro-life Democrats are shoo-ins for reelection: Daniel Lipinski (IL-3) and Collin Peterson (MN-7). Henry Cueller (TX-28), recently criticized for his work with Texas Republicans, should also return. Tim Holden (PA-17) and Nick Rahall (WV-3) may face some competition.

"Holding a pro-life stance is toxic in a Democratic primary in most parts of the country," said Matthew Wilson, a professor of political science at Southern Methodist University. "It can be pretty tempting just to give up."

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