They may or may not be legit. But they ring true. Not reporting cash transactions seems exactly what a "libertarian" cow farmer might do. This is an actual person who made her statement under oath, not an anonymous accuser making allegations to left-wing media outlets.
Anyway, with the race so close, there is nothing wrong with something like this being a deciding factor for an undecided voter and I suspect it will with many of them. Why take a chance? Suppose Massie wins on Tuesday. Now he's the Rep nominee. More women may come out of the woodwork. Usually guys like him don't just target one woman for a once in a lifetime getting out of line.