Strategically, this advantage should create an extraordinary opportunity for the American liberal-left. As the standard-bearer for the Democratic party, Clinton is in a position to press this advantage against her political opposition and make them pay as high a price as possible for nominating such an unpopular candidate. Broadly, this would mean, among other things, winning as many legislative seats as possible in order to advance the Democratic agenda.
Instead, we are seeing the exact opposite. From the recent email leaks, DNC Communications Director Luis Miranda:
[T]he Clinton rapid response operation we deal with...[doesn't] want us to tie Trump to other Republicans...That's a problem....we can't give down ballot Republicans such an easy out. We can force them to own Trump and damage them more by pointing out that they're just as bad on specific policies...We would basically have to throw out our entire frame that the GOP made Trump through years of divisive and ugly politics. We would have to say that Republicans are reasonable and that the good ones will shun Trump...It might be a good strategy ONLY for Clinton...The strategy that Miranda is criticizing here is precisely the strategy that we have seen play out over the past few weeks, as the Clinton campaign hypes statement after statement from "reasonable" Republicans who have become embarrassed by Trump. Liberals and Clinton media surrogates have fallen in line accordingly, and are now openly praising Republicans who everyone understood yesterday to be some of the most radical reactionaries on the planet.
Similarly, the leaked emails also revealed that Clinton only allowed state parties to keep "less than one half of one percent of the $82 million raised", ostensibly for them, through the Hillary Victory Fund. That money, routinely praised as Clinton's effort at "raising big money to boost down-ballot Democratic candidates," ultimately ended up back in her own coffers.
There is plenty more to say about how Clinton and her surrogates have taken this election as their opportunity to attack leftist activists, positions, and priorities, but her campaign's relationship with down-ballot candidates is the clearest indication of how she will wield power. Given the opportunity to win back the House and Senate, overcome Republican obstruction, and advance an agenda - not just a leftist or progressive agenda, but an agenda of any kind - Clinton has chosen instead of consolidate her power and maintain the political status quo. She is not only leaving down-ballot candidates to fend for themselves, but is actually placing them in a weaker position by refusing to nationalize this election and turn every Congressional race into a referendum on Trump.