{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
}) as pageInfo, dealEntries %}

{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
   endDate : '>=' ~ now
}) as pageInfo, dealEntries %}

{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
   endDate   : '>= ' ~ now ~ 'or is null'  // but this syntax incorrect
}) as pageInfo, dealEntries %}