I checked FTDNA and found the following in results:
Jefferson Line 1 - Haplogroup T (T-M70>>PF7457>>BY78550)
WT profile Jefferson-2 Peter Jefferson is tested at FTDNA and does in fact appear to be Haplogroup T and is grouped with these additional kits:
Kit 870064 Jefferson
Peter Jefferson - 29Feb1708/17Aug1757
Kit 874718 Jefferson
Thomas Jefferson, b.1629 and d. 1697
Kit MK61038 Jefferson
Kit 874718 does not appear on WT search