COLUMBUS, Ga. — Republicans, poised for strong gains in the midterm elections, are offering starkly conflicting messages about President Obama to rally their voters. In one moment, they say the president is feckless and weak. But in the next, they say Mr. Obama is presiding over an “imperial presidency” that is exercising power that verges on dictatorial.

So far, they are succeeding in having it both ways.

Representative Paul Broun, Republican of Georgia, who has accused Mr. Obama of “leading from behind” on foreign policy, stood before a gathering of Republican women here recently, his voice loud and deliberate, as he raced through a long list of areas where he said the Obama administration has veered “totally out of control” — the health care law, Internal Revenue Service treatment of conservative groups, and the National Security Agency’s surveillance program, to name a few.

As the crowd murmured its assent, Mr. Broun, who is running for his party’s Senate nomination, reached into his black blazer and pulled out the pocket-size Constitution he always carries.

“They’re a symptom of a government that has just totally left the bounds of our U.S. Constitution,” he said, “and the solution is putting this government back on the course that our founding fathers gave us in the U.S. Constitution.”