He doesn't seem to make that claim universally though:
"When the 17th Amendment was ratified and went into effect to make senators elected by the people rather than appointed by the state legislatures, it provided additional reasons to uphold recall where provided. This Amendment repeated, word for word, the language of the basic Constitution that the state voters would be those for "the most numerous branch of the state legislature." It left to the states the definition of who could vote and how the elections would be conducted."
He doesn't seem to make that claim universally though: "When the 17th Amendment was ratified and went into effect to make senators elected by the people rather than appointed by the state legislatures, it provided additional reasons to uphold recall where provided. This Amendment repeated, word for word, the language of the basic Constitution that the state voters would be those for "the most numerous branch of the state legislature." It left to the states the definition of who could vote and how the elections would be conducted."