To paraphrase Mark Twain's observation on weather, everyone complains about the two-party system — but nobody does anything about it. That has long seemed true of routine complaints about the binary nature of America's national politics, which have been stable for more than 150 years. In 2016, however, the appeal of factional politics appears to have caught up with the Republican and Democratic parties — and at just the precise moment when both seemingly have lost the competence needed to stage a simple, scripted convention.

Tensions between grassroots voters and the party leadership nearly produced a disaster in last week's Republican convention. Despite their defeat in the primaries, so-called #NeverTrump delegates attempted to pass a series of reforms in the Rules Committee, including a rule that would allow delegates at future conventions to "vote their consciences" — in other words, ignore direct democracy. That only attracted a handful of votes in the committee meeting leading up to the convention, but the desire to make a statement about the rules during the main event didn't die with those proposals.

Nine states issued petitions last Monday with majorities of their delegations that called to have the final Rules Committee report handled by roll call vote rather than acclamation. The intent was to offer a momentary protest, allowing the dissenters to have their say, which in this case would have done nothing to stop the march to a Trump nomination. Such a parliamentary move only required seven states. Rather than allow it, the RNC quashed the effort, reportedly by twisting enough arms to get four states to withdraw the petitions.

Delegates became outraged — including some Trump delegates, who thought the RNC had overreached. Rather than defusing the tension, the intervention caused the wound to fester until Wednesday night, when Ted Cruz took the stage. Few expected the runner-up to endorse Trump, but few expected him to provoke the still-simmering resentment by telling voters to "vote your conscience" up and down the ticket, a clear reference to Monday's squabble and the RNC's heavy-handed intervention. The floor-fight resentment spilled out into the open in prime time, turning the traditional Unity Festival into a colorful demonstration of a deeply divided party.

The Democrats delighted in gloating about the GOP chaos.

Oops.

This week has already arguably been worse for the Democrats than last week was for the GOP. And it's only Tuesday.

DNC chair Debbie Wasserman Schultz has been tossed out of her own convention and forced to step down as DNC chair. Top Democrats got booed at warm-up events across the spectrum — and even at the convention itself.

It started with a hack of the DNC email system and the exposure of messages that showed top officials strategizing to undermine Bernie Sanders' campaign. An exchange between DNC CFO Brad Marshall and CEO Amy Dacey proposed highlighting Sanders' lack of Jewish practice and hints of atheism (which Sanders later denied) as a way to push Southern Baptists into Hillary Clinton's column. "It's these [sic] Jesus thing," Marshall explained in a follow-up, to which Dacey replied "AMEN."

Sanders' supporters immediately declared this proof of establishment meddling in their direct-democracy process. Wasserman Schultz had already long been in their sights as the DNC official most to blame. By Sunday, she tendered her resignation, but still planned to gavel in the convention on Monday — until a meeting with her fellow Florida delegates turned into a disaster. Booed off the stage, and with a number of prominent Democrats suggesting she rethink her convention appearance, Wasserman Schultz slunk off to Florida.

But she was hardly the only Democrat to get a hostile reception from supposedly friendly crowds. House Majority Leader Nancy Pelosi also got booed at the same Florida meeting by Sanders' backers for urging party unity at the upcoming convention. Remarkably, the same thing happened to Sanders himself Monday afternoon, while telling a crowd of supporters, "We have got to elect Hillary Clinton and Tim Kaine," turning a big cheer for Sanders' anti-Trump preface into a cascade of boos and catcalls.

The lesson from both the Republican convention and the disastrous start of the Democratic convention may well be that the much-predicted end of the two-party system has all but arrived. Both parties have traditionally acted as so-called big tents, where factions have always contended for primacy. In the end, though, party regulars — the agents of representative democracy — understood that unity after a primary boosted everyone's access to influence and power, and held populist passions in check to ensure the best possible broad front for general elections, both for the White House and for Congress.

Now, however, the populists — agents for direct democracy — in both parties may be ready to break those ties and remain independent factions rather than yoke together for a common goal. If so, few have more responsibility for that than Bernie Sanders, who offered a chagrined response to the boos that naturally flowed from his populist "revolution," and Ted Cruz, who made ideology not just superior to unity but made cohesion itself evidence of betrayal. They may well have made themselves obsolete along with the two-party system they long decried. And if one of these parties can figure out how to come together for one last hurrah, they may take it all in 2016.