Rahm Emanuel was agitated. The opportunity to pass President Obama's top domestic priority before year's end seemed to be slipping away. It was early November. The Senate was taking too long. With Democratic senators and aides gathered in a conference room, the White House chief of staff wanted to know: Was there a chance the...

WASHINGTON — Rahm Emanuel was agitated. The opportunity to pass President Obama’s top domestic priority before year’s end seemed to be slipping away. It was early November. The Senate was taking too long.

With Democratic senators and aides gathered in a conference room, the White House chief of staff wanted to know: Was there a chance the chamber could act in the seven weeks before Christmas?

For Emanuel, an impatient man and conditioned by years of service in the faster-paced House, the Senate’s sluggish pace was maddening. Sen. Charles Schumer, D-N.Y., told him there was one chance: The White House would have to put its trust into an unlikely vessel — Majority Leader Harry Reid.

A quirky Nevadan with no background in health policy and a less-than-commanding public image, Reid may not have inspired instant confidence. But Emanuel agreed. And having united his caucus and blocked a series of Republican filibusters, Reid today is delivering on the most sweeping health-care bill to move through the chamber in nearly half a century.

His effort at times revealed an unseemly side of congressional business as he struck bargains with senators who traded votes for aid to their states. Deals always have been part of how Congress operates, but this battle occurred in a fishbowl of public scrutiny — giving Republicans a fat target for attack.

“This bill is a mess, and so is the process that was used to get it over the finish line,” Senate Minority Leader Mitch McConnell, R-Ky., said this week in a taste of what figures to come as the 2010 midterm election season begins.

If the process opened the Democrats to criticism, it also revealed that the oft-fractious party could achieve unity. And the key was two particular qualities Reid possesses in abundance: an unparalleled understanding of the arcane institution he leads and a grasp of the particular needs of the lawmakers who serve there.

“So many people find Harry Reid incomprehensible as a leader in large part because he is so unprepossessing as a public speaker,” said Ross Baker, a Rutgers University political scientist. “There are Senate leaders … who come along every few decades, who really know the ins and outs of the chamber and have an intuitive understanding of the political sensibilities of each of their colleagues.”

In the end, Reid persuaded public-option purists to accept that their holy grail was out of reach. He led reluctant Democrats to cave to drug-industry interests. The most ardent anti-war member voted to move a war funding bill to make it possible to return to the health-care debate.

But in the eyes of the majority leader and his party, the payoff was a huge accomplishment: The $871 billion bill, paid for with a mix of tax hikes and Medicare cuts, would expand coverage to an additional 31 million people in the next decade while beginning to change the way that Americans get health care.