article.modalMembers {
  -webkit-columns: 2 200px;
     -moz-columns: 2 200px;
          columns: 2 200px;
}

/* or */

article.modalMembers {
  -webkit-column-count: 2;
     -moz-column-count: 2;
          column-count: 2;
  -webkit-column-width: 200px;
     -moz-column-width: 200px;
          column-width: 200px;
}