A divided Senate on Thursday derailed Democratic legislation providing $21 billion for medical, education and job-training benefits for the nation’s veterans, as the bill fell victim to election-year disputes over spending and whether to slap sanctions on Iran. With each party coveting the allegiance of the country’s 22 million veterans and their families, Republicans and Democrats blamed each other for turning the effort into a chess match aimed at forcing politically embarrassing votes. Republicans used a procedural move to block the massive bill after Senate Veterans Affairs Committee Chairman Bernie Sanders, I-Vt., chided GOP senators for their priorities. …