But the dynamic, which Democrats largely blame Republicans for, has irked many of them, especially on the Hill. “I think it is unprecedented of a leader in the Senate of either party to say the most important goal he has is to make the current president a one-term,” said Senator Barbara Boxer, Democrat of California. “That is about respect, that is about priorities and it is just wrong.”

Julian E. Zelizer, a political scientist at Princeton, said that when it comes to Mr. Obama, Republicans “just keep gaining confidence to force his hand.”

“While there might be a few people whose words have become nastier than usual, I think this is really the new normal in Washington with a president who is always on the ropes,” Professor Zelizer said. “I am not convinced that is about lack of respect so much as the feeling that this is a weak president. If the president seemed more powerful they would have returned the call.”…

There is the persistent and deeply uncomfortable question of race. Many African-Americans, including black lawmakers, and even white Democrats, have complained that some of the disrespect for Mr. Obama stems from distaste among some whites at the idea of seeing a black man in the Oval Office.