Suppose you were someone who wanted to consolidate a great deal of political and economic power. In a dictatorship, your path would be clear: become dictator and use central control of all institutions (police, army, media, etc.) to assert your dominance. In a democracy, however, that's harder to do, because the electorate can fail to elect you or can vote you out.

One way to avoid that fate is to control the facts. That is, your goal is not to diagnose and solve real problems; it's to consolidate power. So, when a fact gets in your way, you must be able to dispense with it.

Just to pull a wild example out of the air, take Donald Trump. A core message of his demagoguery is that the economy is terrible. So he claims that the real unemployment rate is 40 percent instead of the about 5 percent the Bureau of Labor Statistics (BLS) says it is. Now, we can have good arguments about how representative that 5 percent rate is of the actual slack in the job market, but there's no question that the BLS does a fine job measuring the concept that it has called unemployment for generations (that is, the share of the labor force looking for work). Nor is there any question that, while there's still slack in the job market, the unemployment rate has fallen by half, from about 10 to about 5 percent.

As that's an inconvenient truth for Trump's core message, he must prevaricate. This is a very common practice for the candidate, who was once "shown to lie more than 70 times in a single event," New York Times columnist Tim Egan wrote, citing a Huffington Post story.

All of that is pretty obvious, out there in the open for all to see. But what you don't often see is something even more nefarious: the quiet, systematic attempt to defund our statistical agencies, including the Census Bureau and the BLS. While such efforts are cast as fiscal necessities, that's pretty ridiculous given the relatively small amounts involved. The whole budget for the BLS was less than two hundredths of 1 percent of federal spending last year.

What's really going on here is not just a disregard for facts, but an effort to undermine them at their data-collection source. If nobody has accurate numbers, then nobody can disprove the demagogues' stories.

The most recent manifestation of this issue can be seen in two proposed amendments to the Commerce, Justice and Science appropriations bill that threaten the quality of the 2020 census. One of those amendments, from Sen. Deb Fischer, R-Neb., strikes directly at Census Bureau funding. The proposed $148 million cut would inhibit the agency's ability to modernize its methods of "reaching people, collecting and processing data, and managing field operations." It not only could also result in the elimination of the American Community Survey — a critical source of state and local economic and demographic data — and/or the 2017 Economic Census, but also could actually cost taxpayers money in the long run. That's because reverting to the agency's "outdated census design" from 2010 could carry a $5 billion price tag, as the bureau would have to abandon money-saving technologies, such as online-response options, before they can be tested.

The other amendment, from Sen. David Vitter, R-La., may be even more pernicious. Vitter argues that adding new questions on citizenship and legal status to the survey would result in a fairer, citizen-based allocation of congressional seats for each state. In reality, such questions surely would undermine the accuracy of the census by lowering the response rate among both legal and undocumented immigrants. This change also would present a major logistical problem for the bureau: To test how the new questions affected their results, they'd have to restart their multiyear research and testing processes, wasting millions of dollars.

The good news is that the Vitter amendment may be unconstitutional; as the Supreme Court recently confirmed, there is a "long-standing use of total population" for apportionment decisions based in "constitutional history," and Democratic and Republican administrations alike have long supported inclusive population counts.

For years now, the Congress has existed at the corner of dysfunction junction, with gridlock fueled by hyperpartisanship and with facts on the run. The Trump candidacy is the logical extension of this scenario.

But if — as an optimist, I'd say "when" — the fever breaks and we go back to actually trying to understand the world and the economy within which we're trying to get ahead, we're going to need good data. So we mustn't let the know-nothings have their way. When they come for the facts, we must do everything we can to block them.

Jared Bernstein, a former chief economist to Vice President Joe Biden, is a senior fellow at the Center on Budget and Policy Priorities and the author of the new book, "The Reconnection Agenda: Reuniting Growth and Prosperity." He wrote this article for the Washington Post.