Hillary deliberately timed this announcement to suppress voter turnout in California.

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219. Calling this voter suppression is insulting to the real victims of voter suppression

The people who have faced violence and intimidation to prevent them from voting, who in the past faced poll taxes and other unconstitutional hurdles, and who today are being disenfranchised by ID requirements that are difficult for poor and elderly voters to meet.

No one is preventing a single Sanders voter from going to the polls. If they choose not to go it's entirely on them. The reality is that they have exactly the same reason to go today as they did yesterday. Sanders strategy was and still is to win as many contests by as large a margin today as possible thereby cutting into (but almost certainly not erasing) Clinton's pledged delegate lead. His strategy then involves taking the results from today along with GE polls to the SDs in an effort to persuade them to switch.

That strategy is unaffected by yesterday's announcement particularly since it was widely reported on Sunday and Monday that Clinton was so close to having a combined total of pledged delegates and SDs that it was inevitable that she would be proclaimed the presumptive nominee as soon as New Jersey (a state Sanders admitted he isn't going to win) was called.

So if Sanders voters stay home the only explanation is that they're low information voters who never understood what Sanders' game plan was or their fairweather supporters -- hardly the revolutionaries they've been depicted as.