Now that Mitch McConnell has caved on the earmark ban, it's worth revisiting the question of why he so vigorously opposed it in the first place, given that he was clearly doomed to fail. Yes, he likes to bring home the pork, but he doesn't need to bring home pork to safely win re-election as long as he desires. I previously suggested that opposition to earmarks represents a species of good government reform that strikes at the core of McConnell's essence.
Another reason is that President Obama supports the earmark ban. And McConnell's strategy is to deny Obama Republican support for any element of his agenda, thereby rendering Obama a partisan figure and reducing his chances for reelection. Indeed, supporting the earmark ban is a cheap, nearly symbolic move that carries disproportionate weight with the voters. Obama is going to be able to boast that joined with Republicans to ban on the historic practice, and that boast will help his reelection prospects. No wonder McConnell tried to stop it.