I keep seeing these polls quoted in the media. For example on CNN, "Sixty percent of Clinton supporters said they would vote for Obama, but 17 percent said they would vote for Sen. John McCain, the presumptive Republican nominee and Obama's rival in the general election. Nearly one-quarter, 22 percent, said they would not vote at all if Clinton were not the Democrats' nominee."
How were "Clinton supporters" defined in these polls? How many of these are Republicans or independents who voted for Clinton in the primary? Why don't any of these stories clarify this issue?