https://uselectionatlas.org/RESULTS/state.php?fips=29&year=2004&f=0&off=5&elect=1Claire McCaskill was born in Rolla (Phelps County), which she won 54/43.
She grew up in Houston, MO (Texas County). She won Texas Co. 64/33.
And she also lived in Lebanon, MO (Leclede County). She won Laclede 63/34.
Then she lived in Columbia (Boone County) where she was homecoming queen at Hickman High School. She won Boone County 63/33.
She was the county prosecutor in Jackson County, and she won 51/46.
So go figure that she won huge margins in the places that she grew up in, but not in regions that she represented as a prosecutor. She also lives in St. Louis now, which she lost to Holden.
In
1998, she won huge margins in Laclede and Texas Counties, along with larger margins in the KC area.
Holden is a Shannon County native, he won that county 53/42. Holden is also a St. Louis resident, and he won there.
Conclusion: Live in many places, it'll help in statewide primaries.
But, that's info that has reached you all too late.