WASHINGTON  Representative Joe L. Barton had to be truly sorry by the time he apologized for his apology on Thursday.

In the four hours between his televised apology to BP  for what he called a $20 billion “shakedown” by President Obama for loss claims in the gulf oil spill  and his apology for that apology, Mr. Barton, a Republican from Texas, had been pummeled in the blogosphere, assailed by Democratic Party operatives and Vice President Joseph R. Biden Jr., and, in the blow that landed, threatened by Republican leaders with being yanked from the party’s top seat on the powerful House energy committee.

By day’s end, the Barton sideshow had become the main show in Congress, eclipsing the much-anticipated grilling of BP’s chief executive, Tony Hayward, by members of the House Energy and Commerce Committee.

“I’m ashamed of what happened in the White House yesterday,” Mr. Barton said in his opening statement. “I think it is a tragedy of the first proportion that a private corporation can be subjected to what I would characterize as a shakedown  in this case a $20 billion shakedown.”