* Donors push Mali to hold post-war vote on July 28 * New government must tackle graft, rebuild shattered state * Botched vote could hinder reconciliation By David Lewis and Adama Diarra DAKAR/GAO, Mali, July 12 (Reuters) - Mali's presidential hopefuls kicked off campaigning this week for a July 28 election intended to draw a line under a coup and an Islamist uprising, despite concerns that a rushed poll may sow the seeds of future strife.