CHARLOTTE, N.C.— President Barack Obama has had harsh words for Congress, and no doubt there are more ahead as the campaign unfurls. So House Democrats have a simple message this week: Don’t blame us. House Democratic leaders have been trumpeting their accomplishments in an effort to inoculate themselves from attacks on Congress and to set themselves apart from the dismal pubic perception of the institution as a whole. In fact, Democratic Caucus Vice Chairman Xavier Becerra (Calif.) said, there is a distinction to be made. “I don’t think the president is running against Congress,” he said. “The president is running...