What makes the 1980 election relevant today is that it was the last national election and the only postwar election where a Democratic president widely perceived to have failed chose to run for re-election.

Both the 20th and 21st centuries have seen failed presidencies.

William Howard Taft lost in 1912, though he might have retained office had not his old friend and former leader Theodore Roosevelt run as a third party Bull Moose candidate and won more votes than Taft.

Herbert Hoover failed through no fault of his own. The Crash of 1929 and the Great Depression were beyond his control, and every remedy he tried failed adequately to work.

Had the popular Cal Coolidge sought a second full term in 1928 instead of declaring, “I do not choose to run,” he would have been in the White House when the crash came and cast by history in the role assigned to Hoover.

But, as one wag said, Silent Cal’s career seems to have been a product of repeated celestial interventions.

By 1952, Harry Truman was a failed president. His approval rating was below 25 percent. Chiang Kai-shek’s China had fallen to communism. Josef Stalin had stolen the secret of the atom bomb through espionage against the United States. Truman had fired Gen. Douglas MacArthur and was in the third year of a Korean War he could neither win nor end.

The administration had been exposed as shot through with corruption and treason in the persons of Alger Hiss, Harry Dexter White and the Rosenberg atomic spy ring, among others.

Rejected in New Hampshire, Harry wisely chose to pack it in.

Lyndon Johnson, his 44-state landslide in 1964 and Great Society notwithstanding, was by 1968 a failed president being repudiated in the primaries of his own party.

Truman and Johnson quit rather than run again and risk defeat.

But Jimmy Carter, whose poll numbers fell as low as Truman’s and who was widely seen as a failed president, chose to fight Teddy Kennedy in the primaries and Ronald Reagan in the general election.

Carter had one signal achievement: the Israeli-Egyptian peace treaty.

But by 1980, he was presiding over an economy with 21 percent interest rates, 13 percent inflation and zero growth. The Soviet Empire had annexed Afghanistan and was on the move in Africa, the Caribbean and Central America. Iran had fallen to the mullahs. Fifty American embassy personnel were being held hostage in Tehran.

What makes that 1980 election relevant is that it was the last national election and the only postwar election where a Democratic president widely perceived to have failed chose to run for re-election.

And what strategy did the Carter campaign adopt?

They sought to demonize Reagan as a tool of the rich, a cold-hearted wretch who would savage the safety net, a crazed anti-communist Cold Warrior whom it would be dangerous to entrust with nuclear weapons. Ronald Reagan was Barry Goldwater redux.

Yet, looking back, what else could Carter do? Looking forward, what else can Barack Obama do?

By 1984, Reagan could credibly run for re-election on the slogan, “Stay the Course.” Let us continue on this path that is leading us to the sunny uplands of a new prosperity and a stronger, more respected America.

Carter could not do that in 1980. Hoover could not do that in 1932. And Obama cannot do that today.

With the nation believing Carter had failed by the fall of 1980, and prepared to remove and replace him, Carter had one lane left to victory. He and the liberal media had to define Reagan for the electorate as an uncaring extremist and dangerous man.

Lest we forget, this Carter strategy was working.

Not until the late debate with Carter did the electorate take a closer look at Reagan and decide that this genial, principled conservative was no threat, but an acceptable alternative and far preferable to four more years of Carter.

After that debate, the undecideds came down hard for Reagan, millions of Democrats switched to him, and he buried Carter.

Again, that election is relevant because it is the election most similar to this one. We have a Democratic president who has presided over a huge loss of jobs, four straight trillion-dollar deficits and 42 months of unemployment over 8 percent. With Obama’s approval in the 40s, it is clear that America is ready for a change.

One difference between 2012 and 1980? President Obama retains a reservoir of goodwill President Carter never acquired.

If this analysis is correct, the Democratic convention and the next nine weeks will witness one sustained slander of Mitt Romney and Paul Ryan as Ayn Randian agents of a plutocracy hell-bent on seeing its taxes reduced and the tax cuts paid for by eviscerating programs on which America’s poor and the working and middle class depend for survival.

The one sure way Obama can win is to convince a nation ready for change — to fear, loathe and recoil from the proposed agents of change.

Obama aides and media auxiliary have already painted the Republican convention in Tampa, Fla., as permeated with lies and dog whistles to racists.

Yet, one wonders: After such a campaign, how does Obama unite and lead the country should he win.