McGovern's big blip in the polls came earlier than Dole's post-convention gain.
McGovern's screw up in the polls happened earlier than Dole's post convention gain in the polls 
mnli hypothesis: McGovern's screw up in the polls happened earlier than Dole's post convention gain in the polls  premise: McGovern's big blip in the polls came earlier than Dole's post-convention gain.