Officials expressed optimism they had finally lined up the support needed to pass President Barack Obama’s top domestic priority.

A vote was expected on the legislation today, after Obama’s scheduled midmorning trip to the Capitol complex to make one final pitch for its approval. The bill is designed to spread coverage to tens of millions who now lack it and ban insurance industry practices such as denying coverage on the basis of pre-existing medical conditions.

Under the arrangement, Reps. Bart Stupak of Michigan, Brad Ellsworth of Indiana and other abortion opponents were promised an opportunity to insert tougher restrictions into the legislation during debate on the House floor.

The leadership’s hope is that no matter how that vote turns out, Democrats on both sides of the abortion divide will then unite to give the health care bill a majority over unanimous Republican opposition.