BEDFORD, Pa. (AP) _ A computer salesman challenging Rep. Bill Shuster in the Republican primary is carrying out a different kind of campaign _ a 500-mile walking tour of the congressional district.

``I think anybody who wants to be a congressman should have to break a sweat, and I'm breaking a sweat,'' said David Keller, 32.

Keller faces an uphill battle against Shuster, who has just returned from a high-profile trip to Afghanistan.

He also faces the possibility that some of his miles of walking will have been in vain. A court ruling last week invalidated the state's current congressional districts, and Republican legislative leaders are still appealing to avoid having to redraw the lines.

The unique campaign is already beginning to wear on the young candidate, who took a two-month leave from his job.

``I think it's a shinsplint,'' Keller said from a road in Reels Corner in southwest Pennsylvania. He has been hopscotching between his walking route and his Chambersburg home each day with his father accompanying him in an aging station wagon.