The condition is based on the situation you're trying to solve. You have not provided detailed explanations on how you expect this to work, so I have only been able to give abstract suggestions so far.
An idea from a colleague of mine:
Add a parameter to the data page, which is a "count"
Use When rules to filter (choose) the Data Source on the Data Page based on the count parameter
When rule for first Data Source is true when count is 0
When rule for second Data source is true when count is 1
The logic that calls the data page will check for failure, and up this parameter, then call the data page again with the new parameter value