Scrambling before showtime Politico has two pre-DNC convention stories worth examining. The first by past convention planners provides a back-stage look at the frenetic preparations for a convention that is at once a four-day infomercial for the Democratic nominee for president, and a last-minute scramble to re-write the script for a convention planned around a different candidate. How to make it must-see TV when everyone knows the outcome? It’s “like herding (childless cat ladies’) cats“: That’s why at this convention, you will see at least one “must-cover” speaker each night: President Joe Biden and Hillary Clinton on Monday, President Barack Obama on Tuesday, President Bill Clinton and Governor Tim Walz on Wednesday, and Vice President Kamala Harris on Thursday. Even with big names, a Democrat supporting a Democrat isn’t newsworthy, but much like a 1970s sitcom, extra-special guests are — especially Republicans supporting Democrats. This is why conventions have tried to highlight unlikely supporters or allies. If it’s rare to have a union president show up for the Republicans (as Teamsters President Sean O’Brien did this summer), it’s also rare to have a CEO show up for Democrats, which is what happened when Costco CEO Jim Sinegal spoke in 2012. Mike Bloomberg vouched for Hillary Clinton in 2016, and Republican Governor and EPA Administrator Christine Todd Whitman spoke as part of a group of Republican women in support of Biden at the 2020 Democratic Convention, as did Ohio Gov. John Kasich. Who will be the unlikely guest star for Democrats this year? Liz Cheney? Paul Ryan?…