Kill 'em both off? Simple! And no nuclear war required!
Let's say on or about October 1st, 2016 an "anonymous hacker" releases a series of videos to the various media outlets across the globe. Due to the Digital Age, such a distribution could be both simultaneous and world-wide thus guaranteeing that the content of the videos could not be suppressed by any one or several biased media outlets.
The content of these videos reveal the clandestine meetings which took place in early 2015 between Donald Trump and Hillary Clinton and... Barack Obama.
In those meetings, the world learns, Hillary and Obama extort & persuade Trump to run for the presidency on the Republican ticket with the predetermined intent of his "throwing" the race to Hillary. The carrot and stick offered to induce the Donald's participation is yet more multi-billion dollar real estate deals he'd been unable to win himself AND also the threat of exposing a secret Trump had thought he'd securely paid off to keep buried. That secret being that Trump's son, Donald John "Don" Trump Jr., managed to kill off not just the son of a Russian mafia boss but his daughter as well when "Don" drunkenly drove them off the road one night in New Jersey. Trump had paid off the local police - handsomely - to make it appear as an hit and run with the negligent driver still at large. The Obama administration learned of this through its NSA surveillance that noted a disparity between the initial police report and the final filed version. Hence Obama's involvement and hence Hillary's since she too has "dirt" on Obama that she is using in her current White House bid.
To say these videos are politically devastating would be understating things. Particularly once its revealed that the videos were originally recorded by Trump himself and only later acquired through NSA snooping. Their release is proof of massive electoral fraud on Trump's part and on Hillary's part. It's also proof of criminal extortion Obama's part. That political firestorm sears through the Democratic Party like little else. The Bernie Sanders supporters demand that Hillary's victories be invalidated and that Bernie be put on the ballots instead. Ballots which are already printed and too far in the process to legally revise.
On the Republican side, the revelations of Trump's deceptions cause their own firestorm within the GOP as his candidacy is declared illegal and Ted Cruz is put forward as they just and legal victor who should be the party's nominee. The infighting there reaches a fever pitch.
Topping it all however, comes the ensuing Trump revelations.
Upon the secret of "Don's" manslaughter being revealed, that Russian mob boss exacts his bloody revenge and suddenly Donald Trump is left without heirs. And he is left without a business empire either as one after another of his loans are called in by former partners who realize that Trump had likely recorded their dealings as well. Once a rush starts like that it becomes a panic as investors desperately try to recoup their loans while there's still any collateral left. In a veritable blink of an eye, Donald Trump's entire life is brought low. His family murdered in revenge, his business empire stripped away from him, and also facing criminal charges for electoral fraud, Trump decides he's nothing left to lose and releases all the rest of his decade's worth of secret recordings and evidence of the dirty dealings he's done.
Dealings with Republicans and Democrats both.
In the span of just a few weeks the leading candidates of both the Republican and Democratic parties are completely discredited and ruled illegal. The parties themselves are revealed as horribly corrupt enterprises as the Trump revelations inspire further such "data dumps" on other politicians otherwise unconnected to Trump or Hillary.
While not happening in time for alternative candidates to emerge in force, the general sentiment of "throw 'em all out" is the rule of the day come the election. And that mood becomes the dominant political force in American politics as each new revelation of corruption and malfeasance just drives the fever pitch ever higher. Hundreds and then thousands of incumbent politicians at all levels of government see the mobs forming and opt to retire before the next set of revelations catches up to them. It makes for some truly spectacular 2018 mid term elections and leaves the political arena of 2020 with both the Republican and Democratic parties mere shadows of their former selves and both desperately trying to reclaim some degree of legitimacy in the eyes of the voting public.