Originally Posted by Sam-Nary
That sounds as though the book is making some commentary on the fact that while Adams and Jefferson and FDR/Truman and Eisenhower were both on different parties that had different viewpoints for the govenment... there was no apocolyptic change that occured when Jefferson took over from Adams and Ike took over from Truman.
After all, it could be argued that the Louisiana Purchase was a "continuation" of Adams' policies in the sense that it didn't strictly follow the US Constitution but used the elastic clause (which Jefferson to my knowledge had heavily criticized). And in time, after Jefferson's presidency was over, he and Adams largely settled their personal differences and put aside partisan politics.
The Louisiana Purchase used the 'shut up and don't talk about it' clause, IIRC.
Jefferson's election did represent a direction shift, but it's very true that the Jefferson of 1805 was not the Jefferson of 1795, and certainly not the Jefferson of 1785.