evidence: But recently, President Biden has been avoiding climbing up the sometimes-wobbly 18-foot staircase that is trucked over to the plane's upper door. More often than not, he is using a much shorter and sturdier set of stairs that fold out from the belly of the plane. Biden, 80, has stumbled on the tall stairs more than once. The short stairs have the distinct advantage of moving most of Biden's ascent into Air Force One out of public view. But for those who have noticed the shift, it also draws attention to one of Biden's greatest political liabilities as he seeks reelection: his age. [...] Democratic operatives charged with setting up logistics and details for Biden and former President Barack Obama confirmed there's been a shift in how Biden boards the plane, but they didn't want to talk on the record for this story, due to the sensitivities around Biden's age.