The Republican Party has proved itself utterly incapable of offering a compelling positive vision of the country's future. And so, in what may be the least surprising political story of the week, McClatchy tells us that GOP strategists plan to make the 2018 midterm elections into a "referendum on the media."

Republicans aren't alone in their ideological disarray and embrace of negative partisanship. Democrats are guaranteed to highlight the stunningly unpopular President Trump in their own 2018 campaigns, hoping that the focus on the awfulness of the Republican in the White House will distract Democratic voters from the absence of a positive message that's proven impossible for the party as a whole to affirm.

It may be the central paradox of our political moment: At a time when the ideological coherence of both parties is in the process of breaking down, we also see extraordinarily high levels of political tribalism, with partisan loyalties persisting and even growing stronger over time.

If our electoral system didn't strongly favor the creation and persistence of two major parties, we might see one or both parties breaking apart before our eyes. The GOP would likely split into populist-nationalist and plutocratic-internationalist parties. The populists would support single-payer health care, while the plutocrats would favor market-based reforms. The populists would back tax hikes on the wealthy to preserve retirement benefits, while the plutocrats would double down on upper-income tax cuts. The populists would try to close the border, while the plutocrats would opt for open labor markets. The populists would be happy to withdraw from our treaty commitments in Europe and around the globe, while the plutocrats would prefer to continue providing for the peace and stability of the liberal international order.

On the left, we'd see a parallel rupture between neoliberals and democratic socialists — with the former favoring open markets, free trade, modest tax hikes, pragmatic reforms of government programs, and piecemeal efforts at regulating additional areas of the economy, while the latter would embrace major new government spending and programs, sharp tax hikes, increasing regulation, and skepticism about open markets and free trade.

Those are the ideological cleavages that increasingly define the Republican and Democratic parties. Yet the cleavages haven't widened into outright splits (at least so far). Why not? Because the leadership of each party recognizes how destructive it would be, badly dividing the vote on one side of the political spectrum and ensuring the victory of the still-unified party on the other side.

That's where negative partisanship comes in.

While voters in each party's electoral coalition are growing more deeply divided about a growing range of issues, it is still possible to unify them in opposition to the evils of the other party. That's what the leadership of both parties increasingly relies on to turn out the vote and generate enthusiasm for candidates.

It's easy to understand why. Those who run the parties have a lot to lose, in terms of power and influence, by allowing them to fracture. Plus, party leaders often personally feel the ideological antipathy to the other party that they seek to encourage as part of their electoral strategy. It all seems perfectly natural: They desperately want to win, and negative partisanship is the surest way to accomplish the goal.

But here's the thing: The goal of a political campaign may be to win, but the point of winning is to govern. And opposition to the other party isn't a governing agenda, as the House GOP has been learning the hard way since January. It might feel good and pay dividends at the ballot box to promise a quick and easy repeal of the other party's health-care reform law, but once the electoral victory has been achieved it becomes necessary to commit to an alternative.

What if the party is too riven by ideological disagreements to form a consensus about what that alternative should look like? And what if the negative partisanship that produced the electoral victory had the effect of papering over that lack of consensus and deferring a necessary confrontation with its consequences? In that case, the party's electoral success will prove to be hollow.

That doesn't necessarily mean the party will be forced to face its electoral comeuppance the next time. On the contrary, it's entirely possible to imagine the Republican Congress passing nothing of significance during President Trump's first two years in office — no repeal and replacement of ObamaCare, no tax reform bill, no infrastructure package — while still managing to hold onto both houses in the midterm election purely by running against "the liberal media." On the other hand, it's also possible to imagine the Democrats flipping both houses of Congress in 2018 while hammering away at Trump morning, noon, and night, and never offering a compelling alternative vision of the country and its future.

Such is the magic — and the poison — of negative partisanship. It promises, and often delivers, short-term political benefits to partisans. But those benefits merely put off a reckoning with political reality that cannot be avoided forever. The ideological coherence of our parties is crumbling. Sooner or later reality (in the form of a candidate who unifies one of the parties in a new way) is going to catch up to them, forcing a genuine realignment. When that happens, all the negativity in the world won't be able to stand against the tide.