Complex sentence: A major item on his agenda was the defense of his 1798 Virginia Resolutions, which had in the year since publication received highly critical replies from some other state legislatures, including the New York, Delaware, and the five New England states.
Split into simpler sentences: A major item on his agenda was the defense of his 1798 Virginia Resolutions. The Virginia Resolutions had in the year since publication received highly critical replies from some other state legislatures, including New York, Delaware, and the five New England states.