Mr. Roberts is now desperate to re-establish ties to Kansas and to adjust his politics to fit the rise of the right in the state. But his efforts underscore the awkward reality of Republicans who, after coming of age in an era of comity and esteem for long-term service, are trying to remake themselves to be warriors for a Tea Party age.

In an interview, the three-term senator acknowledged that he did not have a home of his own in Kansas. The house on a country club golf course that he lists as his voting address belongs to two longtime supporters and donors — C. Duane and Phyllis Ross — and he says he stays with them when he is in the area. He established his voting address there the day before his challenger in the August primary, Milton Wolf, announced his candidacy last fall, arguing that Mr. Roberts was out of touch with his High Plains roots.

“I have full access to the recliner,” the senator joked. Turning serious, he added, “Nobody knows the state better than I do.”

That assertion is disputed by Tea Party activists energized by Mr. Wolf’s candidacy.

“In four and one-half going on five years of existence have we been contacted by Senator Roberts or any of his staff? Not once,” said Chuck Henderson, a Tea Party activist in Manhattan, Kan., who mocked the notion of the senator’s “official” residence here.

Mr. Roberts’s race highlights the divisions within the Republican Party that are playing out in primaries across the country at a time when anti-Washington animus is running high and moderate voices have been displaced by lawmakers with conservative positions on abortion, taxes and education.