When I was on ABC’s “This Week” with Republican Senator Rand Paul in 2012, he confidently declared: “When is the last time in our country we created millions of jobs? It was under Ronald Reagan ...”

Of course, that’s not true. There was an even bigger job boom under President Clinton than under Mr. Reagan, and President Obama has now presided over three years of fairly rapid job growth, with 2014 showing the fastest growth since the 1990s. But does this say anything about the presidents in question?

Both the Reagan expansion and the Clinton expansion had much more to do with Federal Reserve policies than anything coming from the White House, and G.O.P. opposition has stymied Mr. Obama’s macroeconomic policy almost from the beginning of his first term. There are presidents, and sometimes there are job booms when they are president, but the booms aren’t their doing.

But it is nonetheless the case that those Democratic booms vindicate liberal beliefs, while the Reagan boom does not, in any way, validate conservative ideology. Why? Because conservatives insisted that the Clinton and Obama booms were impossible.

I’m old enough to remember the cries of doom when Mr. Clinton pushed through an increase in top tax rates in the 1990s. If you were reading the Wall Street Journal’s editorial page or Forbes or listening to Newt Gingrich, then speaker of the House, you might have thought that it was time to sell all your stocks and wait for a depression.

And later, of course, Mr. Obama was going to bring on a hyperinflationary economic collapse with his health reform law and tax hikes at the top.

Needless to say, none of this happened. What the Democratic booms show, in fact, is that you can strengthen the safety net and raise taxes on the wealthy without causing economic disaster.

But didn’t liberals make similar predictions of a Reaganite disaster? Actually, no. As I’ve pointed out in the past, what happened under Mr. Reagan - tight money brought on a severe recession, but the economy recovered once money was loosened, and the intervening period of slack brought inflation down - was exactly what the textbooks predicted. If politics made any sense, Democrats would be celebrating Mr. Clinton in the way that Republicans celebrate the blessed Ronald, and they’d be hailing Mr. Obama as Saint Bill’s second coming.