Have you noticed Donald Trump isn't bragging about his poll numbers anymore?

With Trump down 12 points to Hillary Clinton in the latest Bloomberg poll, all of the clever-dick theories about the strength and momentum of the Trump campaign are disintegrating one after the other. There is no evidence that Trump is changing the configuration of the electoral map. There is no evidence that he is bringing in a huge new bloc of previously disaffected voters — instead it's just the opposite. The theory that a terrorist attack would help Trump? Refuted when his polls continued to tank after the most deadly mass shooting in American history. Even the core "Trump voters," non-college-educated white men, are turning on him. In a recent Washington Post/ABC News poll, 53 percent of them rated Trump unfavorably. Trump has to do light years better than Mitt Romney among this group to win. He's failing, and he's failing faster than any major party nominee in modern history.

The Republican Party should seek to deny him their nomination in Cleveland. Even if it means a messy convention fight in prime time. Even if it hobbles the nominee that eventually replaces Trump.

Their nominee is already hobbled, because he is Trump. Since Hillary Clinton secured the Democratic nomination, it turns out that it was not just a few right-leaning ideologues and scribblers who think Donald Trump is unfit to be president. A significant portion of the GOP's traditional coalition simply will not let Trump represent them. Many elected Republican officials think Donald Trump cannot be trusted with the awesome powers of the presidency. Trump's disloyalty to Republican orthodoxy and the cartoonishly aggressive style that made him electrifying to his core group of primary supporters turn out to be enormous general election liabilities.

Some Republicans are quietly hoping Trump loses in November, and loses badly enough that the party can just move on afterward. But there's a problem with this line of thinking. Trump has shown himself willing and able to inflict more damage on the party even after securing its nomination. He still refuses to bury the hatchet with Paul Ryan and other leaders. He will drag other Republicans to defeat with him, and he will wreck the party's image for years to come.

Besides, there is still a minor risk that some other exogenous event makes Hillary Clinton unelectable. Say a terrorist attack happens featuring weapons from former Libyan dictator Moammar Gadhafi's unsecured stash. Or Clinton has a debilitating but not fatal stroke weeks before election day and simply disappears from the campaign trail. If his past is a preview of his presidency, Trump winning could do more to destroy the Republican Party than a messy convention fight in Cleveland.

Stopping Trump before the convention may not just be the civic-minded thing to do, it may be in the best interests of the Republican Party long term. If Clinton's campaign somehow fails, Trump's failures as president will still belong to the GOP.

Of course, a convention coup is likely to fail. Republicans have been notoriously slow-footed and uncoordinated in responding to Trump. And there are two major obstacles to its success. The first is the moral obligation that convention delegates feel to vote for the winner of their state or district. Trump may have only won a plurality of primary voters, but even if the Rules Committee unbinds the delegates, many will still feel morally obligated to vote for him on the first ballot. If that's the case, Trump will be close enough to prevailing that the effort to deny him may stall out immediately.

The second obstacle is more familiar. His name is Ted Cruz. The Texas senator will come in with the biggest anti-Trump weapons, the loyalty of delegates who are pledged to him and the many party activists who admire him even if they are bound to Donald Trump. Cruz would be essential to organizing any coup at the convention. And as the next leading vote-getter, he would have demands — possibly including the nomination itself. While Cruz may be more electable than Donald Trump, it is by a margin so slim that the risks of a convention coup and riot in Cleveland may not seem worth trying. Many elected Republicans and big GOP donors view Cruz as treacherous and repellent. They won't give his candidacy much more support than Trump's.

Republicans will have to regroup as a party after 2016 anyway. The Trump challenge showed the deficiencies of Republican orthodoxy, and those must be addressed. But in the meantime, the best thing that the party can do is send Trump back to what he does best, welching on his creditors and selling over-priced garbage with his name on it.