1. The polls are tight
In the words of polling savant Nate Silver: 'It's a close election right now.' We are yet to see if Hillary Clinton will get a convention bump (the uptick in the polls that often follows a candidate's extended airing on primetime television). But both national and battleground-state polls show that Donald Trump is now a competitive candidate - and this after he enjoyed only a moderate convention bump of his own.
There was a moment in midsummer when it looked as though the presidential election could be a blowout, with Trump flailing in response to a lawsuit brought against his ersatz university, and his campaign machinery looking not just disorganised but practically non-existent. That moment is over.
2. #NeverTrump never stood a chance
Some leading Republican figures have decided that Trump is so toxic as to be unacceptable as a presidential nominee. A hundred foreign-policy thinkers signed a letter saying so; the political scientist Robert Kagan wrote a scathing op-ed; Weekly Standard editor William Kristol waged a doleful, doomed campaign to find a last-minute alternative candidate; and some senators and congressmen, such as Nebraska's Ben Sasse, have stuck their heads over the parapet to voice their opposition.
But this rearguard effort has not gained the support of anything like the majority of the party, nor, crucially, does it enjoy the support of key Republican office-holders. For RNC chairman Reince Priebus, Trump is 'someone that's going to go to Washington and shake things up'. House Speaker Paul Ryan believes, in starkly utilitarian terms, that 'not supporting the duly elected nominee of our party ... basically helps deny us the White House and strong majorities in Congress'. Senior party figures take to the airwaves after each of Trump's rhetorical excesses to explain them away. Newt Gingrich, for example, claimed in March that Trump's antipathy towards NATO was nothing more than 'the Bush-Rumsfeld position, which is that the Europeans ought to pick up more of the slack'.
Trump has been mainstreamed by men who have decided that a Republican, any Republican - a Republican who might not actually be a Republican, a Republican who might hasten the downfall of the republic - is better than Hillary Clinton. There will be no bipartisan coming together against the Trump threat. This extraordinary election will be fought in the ordinary way.
3. A positive message could fail to persuade Trump voters
One of the many ways in which Trump is an exceptional candidate for president is that he speaks the language of American weakness, not American strength. Trump's public words tell a story of America bullied by China and Russia, hoodwinked by Iran, beset by terrorists, destabilised by protesters, menaced by criminals, and, most importantly, left adrift in a changing global economy.
His opponents, both Republican and Democrat, have reacted much as one might have expected. 'America is already great', President Barack Obama told the DNC in response to Trump's famous campaign slogan. But there is much danger in this approach. One hesitates to draw close comparisons to the Brexit campaign in the United Kingdom, but it is worth pointing out that Remain's warnings of economic catastrophe failed to win over those for whom the British economy had already been personally catastrophic. As Bob Dylan put it, 'When you ain't got nothing, you ain't got nothing to lose'.
Trump has followed generations of demagogues before him in realising that mob fury grows from the sense that a once-mighty country is going to the dogs. Clinton faces a difficult task in acknowledging the prevalence of such feelings, in a country where globalisation and demographic change have left behind a bewildered social rump, without legitimising the dark nativism that accompanies them. She is not helped by the fact that, in substance, her potential presidency looks less like a moment of change or renewal than something close to a third Obama term.
4. There could be more email leaks to come
Whoever was responsible for hacking and then permitting publication of the DNC's emails, there appears to be an actor with advanced cyber capabilities, an interest in damaging Clinton's candidacy, and the willingness to disseminate stolen documents. We can guess, as others already have, that the same actor might have had access to Clinton's private email server while she was secretary of state - or access perhaps to internal campaign emails, or to the emails of prominent Clinton fundraisers and surrogates, or other sensitive materials. It does not take an enormous leap of imagination to think that another damaging document dump closer to the election - the equivalent, say, of the video in which Mitt Romney wrote off 47% of Americans as indolent malcontents - could be decisive.
5. Outrage fatigue is normalising Trump's extremism
Staying on the subject of emails, in an ordinary campaign, a call by the Republican candidate for a foreign country to hack his Democratic rival might have been treated as disqualifying, if not treasonous. But a year of successive Trump outrages - from his anti-Mexican campaign announcement, to his mocking of a disabled reporter, to his egging on of violence at his rallies, to his promotion of a ban on Muslim immigration, etc., etc., ad nauseam - has widened the boundaries of acceptable political discourse in the United States, and not for the better.
The American media is now in a cycle of reporting not so much the content of Trump's calumnies so much as the controversy surrounding them. Not only does this provide Trump with the free publicity on which his shambolic campaign depends, it gives the impression that objecting to naked prejudice in a presidential candidate is something that Democrats, rather than Americans, do. Clinton will need to find a way to incite voters' disgust without appearing partisan, prissy or monotonous, and do so in a way that leaves space in the news cycle for her own campaign themes. Many of Trump's opponents to date have tried to do this; none have yet succeeded.