It is now all but formalized: Hillary Clinton will be the leading candidate in the presidential election against Donald Trump. It is an election which pits a liberal (in the 19th century sense) against a fascist (in the 1930s sense). In an election wherein voters had good access to accurate information and weighed policy, Clinton would probably win an easy victory. But no election anywhere meets that ideal standard, and in Clinton--who possesses dangerously radical ideas about the world--Democrats have an extraordinarily weak nominee.
It doesn't matter that in degree and kind Trump's scandals and misjudgments are worse than Clinton's. It won't matter that some of his claims are fabricated, and that Clinton's sins pale before his own. He'll be able to de-fang many of her claims.
Even in the area where Clinton's supporters believed she was strongest--foreign policy--Trump has almost no record outside of his outlandish remarks to be measured against Clinton's truly abysmal track record on matters of war and peace. I might be far more petrified by Trump’s fascism than Clinton’s liberalism, but her extremist foreign policy views--and the ease with which her supporters have swallowed her violent excesses--are terrifying in their own right.
The fact is, when she calls him reckless with foreign policy, he will say "Iraq?" When she brings up Trump U, he'll ask about Bill's chancellorship of a for-profit college. When she accuses him out being out of touch he'll revive her comments about being "broke" after the White House. When she accuses him of inconsistency he's got a mile-long list of her flip-flops to emphasize. When Clinton says he'll destroy the economy, Trump will reply, "NAFTA? TPP?"
He has already instructed his online trolls to answer claims of racism against him by citing Clinton's "super predator" remarks. And while self-satisfied Clinton supporters have spent the primary season delivering blanket dismissals of Sanders’ supporters as entitled, feeble-minded millennials, Trump has been consistently courting those voters, inviting them into his dangerous fold. For many of Sanders' supporters who are participating in politics for the first time, Clinton's new outreach to them will feel like salt in the wound.
Clinton's supporters contended that Sanders' more leftist politics would have made him an even easier mark for a Republican campaign, but the public's mistrust of Clinton isn't something you can manufacture overnight; it is the result of tens of millions of dollars of attack ads and 20 years of Clinton's own extraordinary flip-flops that don’t seem to trouble any of her high-profile backers in the Democratic Party.
One can’t entirely blame Democratic voters for failing to anticipate Trump’s rise. But there would have been any number of candidates from the party who didn’t bring Clinton’s serial flip-flops, neo-conservatism, and long-term, deep unpopularity with independents, Republicans, and leftist Democrats to the table. If the party hierarchy had not been intent on steamrolling any opposition, and had actually considered the frailty of Clinton’s candidacy, they might have considered that even in the absence of a Trump-like character, running a candidate as fundamentally weak as Clinton against a party lurching towards fascism was a poor choice given the stakes.