BRUSSELS—The European Union on Monday slapped sanctions on Nicaraguan first lady and Vice-President Rosario Murillo and seven other senior officials accused of serious human rights violations or undermining democracy, amid a crackdown on opposition politicians in the Central American country. EU headquarters said in a statement that the sanctions, which include asset freezes and bans on travel in Europe,” are targeted at individuals and are designed in this way not to harm the Nicaraguan population or the Nicaraguan economy.” In the past two months, police in Nicaragua have arrested and detained more than 20 opposition figures and several candidates who might have been able to challenge President Daniel Ortega in elections on Nov. 7. Ortega, 75, alleges the country’s April 2018 street protests were part of an organized coup attempt with foreign backing. He is seeking a fourth consecutive term in the election. Most of those arrested in the crackdown …