Polls show wide unease among Democrats about having an octogenarian atop their 2024 ticket. President Biden’s approval numbers are mired in the low 40s, and there’s little enthusiasm among voters of either party for a Biden-Trump rematch. So “why doesn’t Gretchen Whitmer just run for president?” said Mark Leibovich in The Atlantic. She’s a popular governor who last year crushed a Republican challenger by 11 points in the purple state of Michigan, while flipping the legislature into full Democratic control for the first time in 40 years. She offers a pragmatic liberalism and a Midwestern personability that appeal to centrists and independents. Despite many Democratic colleagues and donors encouraging her to run, Whitmer vows she won’t challenge Biden. But if a crank like Robert F. Kennedy Jr. can poll as…