Rubuta ci gaba ga wannan sakin layi - A watan Janairun 2008, McCaskill ya goyi bayan Sanata Barack Obama a lokacin yakin neman zabensa
don takarar shugaban kasa ta jam'iyyar Democrat, ta zama daya daga cikin Sanatocin farko da suka yi hakan. Ta kasance daya daga cikin fuskokin da aka fi gani a yakin neman zabensa, kuma goyon bayanta na da muhimmanci ga nasarar da Obama ya yi a Missouri a watan Fabrairun 2008. Ta yaba wa 'yarta Maddie cewa ta shawo kanta don tallafawa Obama a fili. An ambaci ta sau da yawa a matsayin mataimakin mataimakin shugaban kasa ga Obama, amma ba a taɓa yin la'akari da gaske ba. Ta yi magana a ranar bude taron Jam'iyyar Democratic National Convention a watan Agustan 2008.