Washington is in full blame-game mode as the federal government moves into shutdown this morning, including facile attributions of blame to national leaders.

The true culprit, however, is deepening legislative polarization, which has its roots in intra-party dynamics playing out in districts around the country. To help voters understand what is happening and why, reporters should go local, providing richer and more detailed coverage of the positions and district politics of the legislators who are pushing the House GOP toward confrontation.

One explanatory frame for the current legislative fight blames squabbling national-level political leaders for failing to make a deal—an easy way to avoid taking a position that could be construed as partisan or ideological. On Twitter, for instance, Time’s Mark Halperin named a variety of political figures from the past as “[p]airs who could negotiate a CR/debt deal: Gene Sperling-Josh Bolten, Bill Clinton-George W. Bush, Ron Klain-James A Baker 3d.” The implication, of course, was that the current negotiators weren’t up to the challenge. Similarly, the Washington Post editorial board condemned the “dereliction of leadership” in Congress and asserted that “the grown-ups in the room will have to do their jobs,” naming the leaders of the two parties in Congress and the President.

In making these points, Halperin and the Post echoed the sort of rhetoric espoused by MSNBC host Chris Matthews in his new book, which credits House Speaker Thomas “Tip” O’Neill and Ronald Reagan for working together in a way that today’s leaders don’t:

They argued mightily, each man belting out his separate, deeply cherished political philosophy—but then they would, both together, bow to this country’s judgment. Decisions were made, action taken, outcomes achieved… During this period, government met its deadlines. Members of Congress listened and acted. Debates led to solutions. Shutdowns were averted…

Today we have government by tantrum. Rather than true debate, we get the daily threat of filibuster… Presidents make ‘recess’ appointments to end-run Senate consent… I truly believe it doesn’t have to be this way… We need leaders able to balance large purpose with equally large awareness of the electorate, what message the voters have sent.

Even if the shutdown is resolved relatively quickly, complaints along these lines seem likely to grow louder in the coming weeks. Though the current debate concerns the funding of government, many observers expect the upcoming debate over raising the debt ceiling—which Republicans are expected to oppose absent significant concessions by Obama—to be even more contentious.

But what this analysis overlooks is that past figures like O’Neill and Reagan operated under structural conditions that were far more favorable for deal-making than those facing President Obama and House Speaker John Boehner today. These graphs by the political scientists Adam Bonica and Howard Rosenthal illustrate the widening ideological divisions between the parties in the House over time (click the image for a larger view):

The increasing divisions between the parties in Congress are contributing to the slow-motion collapse of various institutional norms and procedures that prevailed during the artificially depolarized mid-20th century era, including the tradition (generally but not always observed) of allowing the debt ceiling to be raised with few or no strings attached to accommodate past deficits incurred by Congress and the president.

More specifically, what has been driving this process? Assigning “fault” is a subjective issue that is arguably beyond the scope of a reporter’s duties, but it’s hard to deny that the roots of this fight are in the Republican caucus, which has moved further from the ideological center in Congress than Democrats in recent decades, and in turn embraced more high-stakes tactical maneuvers like using a government shutdown and the debt ceiling for leverage in the current debate. These tactics may seem to broach institutional norms, but they have a clear strategic logic. As Rep. Phil Roe (R-TN) put it, “You have to have some way to negotiate an issue that the other side won’t negotiate with. Running the federal government is one of them. The debt ceiling is another.”

Importantly, though, the Republican party is internally divided over this course of action. The tactics being employed by the leadership are reportedly being driven by a relatively small group of House members—according to the Washington Examiner’s Byron York, for instance, just 30 House Republicans:

[I]nsiders estimate about 30 House Republicans believe strongly that Obamacare is such a far-reaching and harmful law that the GOP should do everything it can—everything—to stop it or slow it down. That includes precipitating a standoff leading to a government shutdown…

Another 20 to 30 GOP members sympathize with that position but might be willing to compromise, except for the fact that they fear a primary challenge from the Right.

Brendan Nyhan is an assistant professor of government at Dartmouth College. He blogs at brendan-nyhan.com and tweets @BrendanNyhan.