Given the example E2 in PDTB, the PDTB annotators explain it as Contingency or Expansion relation and manually insert corresponding implicit connective for one thing or because to express its relation.
arg1:Now the stage is set for the battle to play out arg2:The anti-programmers are getting some helpful thunder from Congress Connective1:because Sense1:Contingency.Cause.Reason Connective2:for one thing Sense2:Expansion.Instantiation (wsj 0118) the ambiguity of implicit discourse relations makes this task difficult in itself.