Here are the possibilities as I see them:
1. John McCain is unaware that the timing of U.S. officials’ trips to Iraq is kept quiet to avoid helping terrorists there plan attempts to kill them.
2. John McCain is so forgetful that he didn’t remember that when McCain said in public that Obama’s trip to Iraq is scheduled for this weekend.
3. John McCain actually wants to help terrorists assassinate Barack Obama.
Since (1) and (3) seem implausible, we’re left with (2) as the least hypothesis.
Should someone that forgetful be seeking the Presidency? I don’t think so, either.
