Conversation so far:
Who was Gavel's running mate?
CANNOTANSWER.
Who did he compete against in 1972?
former Governor of Massachusetts Endicott Peabody had been running a quixotic campaign for the same post.
What significant events happened during the campaign?
At the convention's final day on July 14, 1972, presidential nominee McGovern selected and announced Senator Thomas Eagleton of Missouri as his vice-presidential choice.

Question: What did Gravel do afterward?
Self-contained rewrite: What did Mike Gravel do after Senator Thomas Eagleton became McGovern's vice-presidential choice?