Complex sentence: At the district convention in May, Keith Ellison won the endorsement after Nelson-Pallmeyer withdrew from the endorsement process and threw his support to Ellison, who went on to win the general election.
Split into simpler sentences: At the district convention in May, Keith Ellison won the endorsement after Nelson-Pallmeyer withdrew from the endorsement process and threw his support to Ellison. He later came out in support of Ellison, who went on to win the general election.