On paper, the race for the Republican presidential nomination has been over for quite a while. Donald Trumps remaining rivals quit in early May and hes locked up more than enough bound delegates to win on the first ballot. There is no meaningful doubt as to who the GOP nominee will be.Dozens of Republican convention delegates are hatching a new plan to block Donald Trump at this summers party meetings, in what has become the most organized effort so far to stop the businessman from becoming the GOP presidential nominee. Given the strife, a growing group of anti-Trump delegates is convinced that enough like-minded Republicans will band together in the next month to change party rules and allow delegates to vote for whomever they want at the convention, regardless of who won state caucuses or primaries.Theres no shortage of reasons for skepticism, not the least of which is the arithmetic: the WashingtonPosts report said at least 30 delegates are involved in the effort. There are 2,472 delegates headed to the Republican National Convention. At least 30 is a start, but its safe to say the odds are not in therenegades favor.Donald Trump on Saturday called efforts by a group of Republican convention delegates to prevent him from officially clinching the nomination illegal and a hoax.Mr. Trump, speaking at a campaign rally in Las Vegas, devoted a hefty portion of his opening remarks to criticizing efforts to dislodge him. First of all its illegal. Second of all, you cant do it, he said. You have a couple of guys that were badly defeated, and theyre trying to organize maybe like a little bit of a delegate revolt.Trump is devoting quite a bit of energy to denouncing this little possibility. Hes accused Jeb Bush of being involved in the plot against him; hes publicly mocking the GOP insurgents who failed to derail him during the primary process; and hes insisting that the entire effort is a hoax, thats all made up by the press.Note, some of these complaints are contradictory. The anti-Trump campaign cant be a real thing, orchestrated by the candidates Republican detractors, and a made-up thing, imagined by the media. It can be one or the other, but not both.Just to reiterate a point from a couple of weeks ago, Im reasonably sure there will be no convention coup. Its a fun political thought experiment to kick around, but anyone expecting Trump to face such an organized convention revolt is very likely to be disappointed.Indeed, the possibility of a Republican civil war four months before Election Day may be the only scenario worse for the GOP than a Trump-led ticket.The possibility of a coup might be slightly less ridiculous if there were a plausible candidate waiting in the wings, ready to rally support from the GOPs various factions, and eager to pick up the pieces after a convention coup tears the party apart but no such candidate exists. Trumps critics couldnt figure out how to slow him down over the last 12 months, and theres no reason to believe theyll organize a credible convention challenge over the next month.But given how much Trump is talking about the possibility, the mere threat of a revolt appears to have rattled the presumptive GOP nominee in ways that make him look surprisingly nervous.