WASHINGTON — When lawyers for Texas and 19 other states were deciding where to file a lawsuit seeking to wipe out President Barack Obama’s health care law, they had many choices. But they settled on a federal courthouse in Fort Worth, Tex.

Forum shopping in litigation is common, and liberal lawyers challenging Trump administration initiatives like to file their cases in places like San Francisco or Brooklyn. But the lawyers in the health care case did more than choose a venue where the mix of judges was likely to include ones apt to favor their arguments. They effectively chose their own judge.

That is because there is only one active judge in the Fort Worth Division of the Federal District Court for the Northern District of Texas. He is Judge Reed O’Connor, and he has quite a track record.

He ruled for Texas in 2015 when it challenged an Obama administration measure extending family leave benefits to married same-sex couples. That decision came two years after the Supreme Court extended federal benefits to such couples and just months before the court established a constitutional right to same-sex marriage nationwide.