begins by looking at the demographics on the abortion issue that say you want to win elections you'd better change.

The United States has some of the most permissive abortion laws in the world. Most Americans do not support such policies. Seven-in-ten want abortion broadly illegal after week 12 of pregnancy, about 8-12 weeks before most current state thresholds.

Furthermore, Gallup recently found those “who would only vote for a candidate who shares their views on abortion” is at 21%, the highest number in the 19 year history of their asking the poll question. They also found 23% of pro-life Americans fall into this category, compared with 19% of Americans who identify as pro-choice.

This lean in favor of pro-lifers is likely to get stronger as Millennials come into their own....
Then it gives examples.

Sanders has enough independence from the Democratic Party establishment to call progressives to face the math on these questions and openly support pro-life Democratic candidates in certain districts. Yesterday he was joined by DNC chair Tom Perez in supporting Health Mello, a pro-life liberal running for mayor of Omaha.

The Richards/Hogue Inquisition pounced, bullying the 37 year-old Mello into walking back his pro-life voting history, a practice that is now all too familiar for pro-life Democrats. But it was too late. Sanders and Perez had made it clear that a more realistic wing of the party is fighting back against the abortion extremists who want to take it off a cliff. The runner up for the Democratic nomination for president, and the DNC chair, had openly and firmly supported a pro-life candidate.
Partisans don't really care about priciples.