An Obama precinct captain in Nevada has circulated a flyer that urges Republicans (and independents) to become Democrats just for a day in order to stop Hillary.
The flyer is likely to be controversial, because it's playing on Republican dislike of Hillary to get GOP voters to affect the outcome of the Democratic caucuses.
"Republicans, Independents, Everyone," the flyer reads. "You can make the difference if you think a Democrat will win in November and you don't want Hillary...You can come to the Democratic caucus and vote for Obama."
Though precinct captains are volunteers, they are designated as such by the campaigns. And while this flyer isn't the official work of the Obama campaign, in this race campaigns have been held liable for the actions of such volunteers. When a Hillary county coordinator forwarded a copy of the Obama Muslim smear email, it became national news for days, leading to her resignation.
Here's the flyer in question (click on images to enlarge):

Obama spokesman Bill Burton confirmed that Buchanan is a precinct captain, and sent me this statement:
We've learned that one individual who volunteers for the campaign was making the flyer and weve instructed him to stop creating and distributing it. But make no mistake, we want as many independents and Republicans to become Democrats and help to build a new governing majority in this country.
I just got off the phone with the precinct captain, Bob Buchanan. He said that he had stopped distributing this particular flyer and replaced it with what he called a more positive one.
Nonetheless, Buchanan acknowledged to me that this one attacking Hillary had been distributed.
The new version also appears to play on GOP hatred for Hillary, though in more cautious language. Buchanan confirmed that the new version says:
"Republicans, Independents, Everyone. You can make the difference if you think a Democrat will win in November and you have said anybody but Hillary."
Late Update: The Huffington Post, which had this posted first, adds some more context from Buchanan on the rationale behind the flyer.
Late Late Update: In response to some commenters below, the point of mentioning the Muslim smear email isn't that writing this flyer and distributing it is comparable to forwarding that email.
The point of drawing the comparison, rather, is that it illustrates that in this race the campaigns are being held accountable for the actions of low-level volunteers. The Obama campaign itself knows this, which is why they're disavowing the flyer.