Text stimulus (graph): Scenario chart titled 'Overall support under assumptions about nonrespondents'. X-axis scenarios labeled 'Nonrespondent support 20%', '30%', '40%', '50%', and '60%'. Y-axis overall support from 30% to 70% in 10-point increments. Plotted data: bars at 38%, 44%, 50%, 56%, and 62%. Additional evidence: a horizontal reference line at 50% and note 'Respondent support = 65%; response rate = 40%'. What is the most responsible conclusion?