As Great Britain prepared for war with Germany in 1939, the government printed millions of colorful posters urging the people to “KEEP CALM AND CARRY ON.” The posters never needed to be distributed because that’s what the people were doing, on their own.

It is an example to the people of America right now amidst the uncertainty and unprecedented anxieties surrounding this critical national election.

We need to keep calm and carry on.

Fact: No law requires a conclusive result on Election Day. No state provides one. Any vote totals released are unofficial, subject to formal canvassing procedures in days to follow and to recounts if the returns are very close.

Fact: Contrary to the president’s propaganda, 19 states allow late-arriving mailed ballots to be counted if postmarked on or before Election Day. Most provide specific extensions for ballots from service members and other citizens overseas.

Fact: The Supreme Court’s historical preference is to allow the states to conduct and count their elections with minimal interference. The 2000 election was an outlier that the court stressed would not serve as a precedent.

The advice to keep calm and carry on applies to everyone — not just anti-Trump voters who are eager to have the election over and him gone. His more militant supporters need to cool it, too.

It is much to be hoped that the returns become sufficiently decisive, one way or the other, for both campaigns to accept the verdict of the people without asking the courts to overturn it.

Only once, 20 years ago, did an election go to the Supreme Court, and that involved a genuine issue over a primitive system of punch-card voting in Florida. Had the state’s vote not been infinitely close, neither candidate would have mustered a battalion of lawyers.

It is too early to know whether there will be any such cliffhanger outcomes in critical swing states to precipitate litigation this time. Chief Justice John Roberts has said with sincerity that there are no Republican judges or Democratic judges, only judges.

Another concern is that Republican legislatures in swing states such as Michigan, Wisconsin and Florida might subvert the people’s decisions by appointing the electors themselves.

There are many conceivable ways to delay the certification of votes in critical states as a means of preventing anyone from having 270 electoral votes cast and countable by the key legal and constitutional deadlines. Those are: Dec. 8 for states to make their counts final, Dec. 14 for the electors to vote in their home states, Jan. 6 for Congress to convene in joint session to count the electoral votes and declare the winners, and Jan. 20 for the inauguration of the president and vice president.

Which party controls the houses of Congress will be critical.

One danger is that state court actions could delay enough final vote certifications to prevent an electoral majority. In that event the House would elect the president, the Senate the vice president. The House would vote by state delegations; the Republicans presently control a majority of those, though less than a majority of the total membership. In the Senate, the vote for vice president would be by a simple majority of all the members. That could lead to a president of one party, a vice president of another, and all the games could backfire if the Congress cannot agree by Jan. 20, the Constitution’s absolute deadline. The House Speaker would become acting president.

What this all means is that the role of the American people — the great majority who crave open, honest and fairly counted elections — did not end when the polls closed Tuesday.

Now, we need to bear down on our state legislators, members of Congress and, yes, our judges, to insist that the election be decided in the normal ways that have served us well for so long. Anything else is a clear and present danger to government of the people, for the people and by the people.

Most of all, everyone needs to keep calm and carry on.