Letters to my Editor

Just the letter, with minimal comment:

I have lived under 17 presidents, since Woodrow Wilson. I don't know that I will see anothe r [sic]. Our present president's style is to stride purposefully to the lecturn, jut his chin out, FDR style, and with much rhetorical skill, tell us what we want to hear but rarely see. This is proven.
Think of his campaign and presidential promises, not of his charm. I don't want my descendants to have to wonder at and ruefully pay for my mistakes.

One question: "proven", how exactly?