MADISON, Wis. — Wisconsin Republicans were ‘‘giddy’’ about a voter identification requirement enacted in 2011 that they saw as an opportunity to drive down Democratic turnout at the polls, a former chief of staff to a GOP state senator testified Monday in a federal trial targeting that law and others.

The lawsuit targets more than a dozen changes to Wisconsin’s election law passed by the Republican-controlled Legislature and signed by Governor Scott Walker since 2011. Two liberal advocacy groups and affected voters argue the changes are a violation of the federal Voting Rights Act, the First Amendment, and the equal protection clause.

Their attorney, Josh Kaul, said in opening statements that evidence will show the changes make it harder to vote for college students as well as for blacks, Hispanics, and other minorities who tend to support Democrats.

Assistant Attorney General Clay Kawski, who is defending the laws for the state, said increased voter turnout since the changes went into effect disproves those arguments.

Associated Press