Complex sentence: The resignation in May 1836 of Senator Isaac Hill, who had been elected governor of New Hampshire, left a brief interim opening to be filled by the state legislature, that also had to fill the six-year term to follow.
Split into simpler sentences: The resignation in May 1836 of Senator Isaac Hill, who had been elected governor of New Hampshire, left a brief interim opening to be filled by the state legislature. With Hill's term as senator due to expire in March 1837, the legislature also had to fill the six-year term to follow.