var cur_div = 'leaders_current';
function show_leaders(which) {
  which_div = 'leaders_' + which;
  //cur_div = 'leaders_current';

  $(cur_div).hide();
  cur_div = which_div;
  $(cur_div).show();
  
  
  //new Effect.Opacity( cur_div, { from: 1.0, to: 0.0, duration: 0.5, afterFinish: function(o) {cur_div = which_div}, queue: 'end' } ); 
  //new Effect.Opacity( cur_div, { from: 0.0, to: 1.0, duration: 0.5, queue: 'end' } ); 

}