Politicians have often said they weren't running. Then have a dramatic change of mind because of "overwhelming support" or some similar phrase. In other words, they're compelled to run by others.
As for Liberals "rioting" to "prevent" Trump from running, per S2Ki, I must have missed those headlines. Seems to me it's been the increasingly stiff resistance by the Republicans themselves to a Trump candidacy that's slowed his momentum recently. And Trump's own frequent gaffs, the most recent once again being to attack women.
Yes, actions do have consequences. And if Trump is beginning to stumble, the causative action is his own crazy rhetoric.
But blaming Democrats is equally crazy. They would be happy to run against Trump in November. All the polls show them trouncing him, along with a good portion of the Republican ticket at all levels if Trump's at the top.
Perhaps attacking Trump this early was tactically unwise, until he had the nomination locked-up. But Dems want to soften the target early, and throw mud at all the Republicans along with him in earlier contests.