A few days ago, Donald Trump adviser and confidante Roger Stone laid out a strategy should his candidate arrive in Cleveland without enough delegates to ensure a first-ballot victory. Stone -- whose former business partner, Paul Manafort, now serves as Trump's convention manager -- urged Trump supporters to converge on Cleveland and be prepared to take action:

"We're going to have protests, demonstrations. We will disclose the hotels and the room numbers of those delegates who are directly involved in the steal. If you're from Pennsylvania, we'll tell you who the culprits are. We urge you to visit their hotel and find them. You have a right to discuss this if you voted in the Pennsylvania primary, for example, and your votes are being disallowed."

I'm sure those "discussions" would go well.

Later, given the chance on "Meet the Press" to repudiate Stone's rhetoric, Manafort demurred, instead turning it around by accusing the Ted Cruz campaign of "Gestapo tactics." Other signs are equally ominous.

In Colorado, where a Republican state convention produced 34 delegates for Ted Cruz and none for Trump last weekend, an angry Trump supporter tweeted out the name, home address and phone number of Steve House, the state GOP chairman. That personal data was then retweeted more than a thousand times. The result?

As House reports it:

One of the emails sent to House read:

"All I can say is pray you make it to Cleveland. The fix is in and the American people will eliminate anyone who gets in the way… It would be in your best interest to take a stand and support the American People and trump or you are done. Trump goes independent to ride the nation of scum like you. I would be hiding all family members…Just check out social media."

In Indiana, potential Trump delegates have said that if given the chance, they would back other candidates in later rounds of voting should the convention be thrown open. After those statements were reported in Politico, more death threats began to pour in.

"What I can share with you at this time is information has been referred to the Indiana State Police that alleges threatening emails have been sent to some Indiana delegates that will be participating in the Republican National Convention in Cleveland, OH," said Capt. David Bursten, a state police spokesman. "Presently the Indiana State Police is reviewing the information to determine if it may cross the line of free speech and could be considered criminal in nature."

Put that together with Trump's own rhetoric, his suggestion of rioting should he be denied the nomination and the history of confrontations at Trump rallies and we have the makings of something very ugly.

Oh, and in the latest national polling, Trump has a 13-point lead (42-29 percent) over Cruz. If John Kasich were to drop out, he'd have a lead of 48-38 percent over Cruz. So apparently this kind of stuff has an appreciative audience.