President Donald Trump wants a new census.  

If by this he means a snap-census before the scheduled 2030 survey, he’s demanding that the federal government undertake a gargantuan task with minimal planning and no discernible source of funding.  

In statistical terms, it’d be like launching D-Day with a month’s lead time.  

If the White Queen believes six impossible things before breakfast, that the Census Bureau could pull this off would qualify as one of them.  

The agency couldn’t even competently conduct the last, regularly scheduled census in 2020.  

Given that conducting the census is a core function of the federal government — indeed, mandated by the Constitution — it is outrageous that the last survey missed so badly. 

It undercounted Florida and other red states (as well as Illinois) and overcounted New York and a number of blue states (plus, Ohio and Utah). 

Because the apportionment of congressional seats depends on population as determined by the census, these were highly consequential errors that can’t be allowed to happen again.  

There’s no legal mechanism for fixing it, though. We just have to do better in 2030.  

Trump is also, understandably, chagrined that illegal immigrants are included in the census and declares that, going forward, they “WILL NOT BE COUNTED.”  

Here he’s going to run smack into the relevant legal texts.  

Article I Section 2 of the Constitution refers to “the Whole Number of free Persons,” while the 14th Amendment includes “the whole number of persons in each State.”  

In similar fashion, the US code calls for a “tabulation of total population by States.”  

So it’s hard to see how illegal immigrants can be excluded from the count.  

As it happens, illegal migrants — who make up just a small proportion of America’s total immigrant population — don’t seem to have much of an effect on the partisan breakdown of congressional seats one way or the other.

Although the highest numbers of them live in blue California, they are spread around the country, with large numbers in Texas and Florida as well. 

A change that Trump wanted in the 2020 census was the inclusion, once again, of a citizenship question — highly relevant information that it’s entirely appropriate to ask.  

There was a long period from the 19th century through 1950 when the census survey asked about citizenship. Later, it was relegated to the so-called “long form.”  

Finally the long form itself was axed after 2000 — and today it’s considered a scandal to even think about reviving it.  

Trump’s proposal to ask the question on the 2020 census encountered stiff resistance and the Supreme Court squashed it.  

But in the big picture, non-citizens who are here legally do have a significant impact on congressional apportionment. 

Recent research by the Center for Immigration Studies found that all immigrants (naturalized citizens as well as all other immigrant categories) shifted 14 congressional seats to Democratic states on net in 2020.  

Non-citizens also distort the composition of congressional districts.  

The CIS study found the same number of citizens in the 13 congressional districts with the highest share of non-citizens as in the nine districts with the lowest share of non-citizens.  

In other words, the citizens in those nine low-immigration districts get four fewer representatives than did the citizens in the 13 high-immigration districts.  

It’s one man, one vote — with an asterisk.  

To take an example from Texas, the Democratic-held 33rd district, where non-citizens are nearly 30% of the population, has 208,000 fewer voting-age citizens than the Texas 21st district.  

That means the citizens of the 33rd district have marginally more clout and representation, thanks to a population tilted toward those who can’t vote.  

Ultimately, the way to diminish these effects is to reduce the level of immigration.  

Early indications are showing a large exodus of illegal immigrants since Trump’s election, and that the United States will have net negative migration this year for the first time in a half-century.  

If Trump wants to fully capture the changes he’s effecting in immigration policy, he should indeed want a new census — but let’s wait until 2030. 

Twitter: @RichLowry