Sea-Change
The Law of of the Sea convention is an international treaty that was designed to bring stability to naval trade. While it's a rather wonky issue, it has gotten very strong support as well as very strong opposition. Fortunately, John McCain has appealed to both groups by falling on both sides of the issue.
Flip
John McCain was one of the strongest supporters for the treaty dating back to the 1990s. The Bush administration has also come out in support of this treaty, both parties claiming that stability and navigation rights would be provided to the US Navy. He was even scheduled to speak on its behalf 2003, when he was to testify on behalf of its passage.
Flop
However, the treaty was less than popular with a large number of conservatives who believe that the treaty would threaten US sovereignty. Not coincidentally, McCain withdrew his support. Another principled stand!