He is in many ways the mirror image of his Democratic counterpart, Mr. Reid. Both are experts at the inside game who struggle with the burden of trying to control a political caucus at a time when legislative leaders no longer have the brute power they once had and senators are hailed for acting like mavericks.

Image In meetings with his caucus, Senator Mitch McConnell urged members to continue to play “team ball” — with the team being the Republican Party. Credit... Stephen Crowley/The New York Times

“Mitch tends to play things close to the vest,” said Senator John Cornyn, Republican of Texas.

The extent of Republican unity to date is attributable to some degree to Democratic missteps, as well as to the rise of the Tea Party movement, which has exerted tremendous pressure on Republicans not to do anything that might give comfort to the president and his party.

But it is also testimony to how Mr. McConnell has been able to draw on 25 years of Congressional savvy to display a mastery of legislative maneuvering. Mr. McConnell rejected the criticism that his approach is all about scoring political points by denying Mr. Obama any victories. His opposition, he said, is rooted in a principled belief that Mr. Obama is pushing the nation in the wrong direction.

Building a Strategy

“To the extent that they want to do things that we think are in the political center and would be helpful to the country, we’ll be helpful,” Mr. McConnell said of the Democrats. “To the extent they are trying to turn us into a Western European country, we are not going to be helpful.”

He consistently told fellow Republicans they needed to win back independent voters and lapsed Republicans who, he said, have shifted only temporarily to the Democratic camp. To win them over, he suggested, Republicans should emphasize issues that resonated with them at a time of insecurity, including government spending, debt, government bailouts and terrorism.

The question now is how much of an enduring gain Republicans might get from Mr. McConnell’s blocking strategy. For all his efforts, Democrats could very well pass a health care overhaul in the next week. While he has drawn sharp ideological contrasts that have rallied conservatives after their Congressional defeats in 2006 and 2008, Mr. McConnell is a long way from capturing control of the Senate in November.