So far, the defining word of the Biden era is “trillion.”

The Joe Biden who portrayed himself as a moderate, old school, bipartisan dealmaker during the presidential campaign is now a distant memory.

He’s been replaced by the Joe Biden who is dazzling progressives with his willingness to “go big” — in other words, spend jaw-dropping amounts that would have been unimaginable prior to the pandemic and are still shocking even now.

Why has Biden embarked on a historic spending splurge with nary a whisper of bipartisan support?

Well, Democrats talked themselves into the proposition there basically isn’t any such thing as spending too much money.

Relatedly, the party consensus is Barack Obama went “too small,” with a stimulus package under a trillion dollars insufficient to the scale of post-financial-crisis recession.

Besides, spending is what Biden can actually do — he can pass his stimulus and relief bills under the so-called reconciliation rules in the Senate, requiring only 50 votes rather than the 60 it takes to break a filibuster.

Finally, any Democratic president is drawn to the heroic allure of FDR and wants to measure himself against the New Deal.

Biden had a recent meeting with historians in the White House at which FDR was much discussed. One of the participants, historian Michael Beschloss, told Axios that FDR or LBJ may be the most apt analogue to how Biden is “transforming the country in important ways in a short time.”

There’s no doubt any president who’s a Democrat would envy the sheer amount of dollars Biden is shoveling out the door.

In fiscal year 2019, the federal government, which wasn’t exactly tightening its belt, spent $4.4 trillion.

Biden is on pace to roughly match that with his first two major legislative initiatives — the $1.9 trillion COVID-19 relief bill, and his new $2.3 trillion infrastructure proposal.

The Biden team almost gives the sense it is working backward — starting with a big, eye-popping price tag and then figuring out what initiatives can be thrown in to reach the top-line number.

The schools have tens of millions of dollars sitting unspent from prior relief bills, and here comes another $100 billion to upgrade school buildings in the infrastructure bill.

The states were lavished with $350 billion in the COVID-19 relief bill, even though many of them didn’t lose revenue during the pandemic. Why can’t those dollars be spent on infrastructure?

The new proposal is an infrastructure, drinking-water, broadband, home-retrofitting, manufacturing, long-term-care, electric-car, unionization bill — and a few other things besides.

The question is whether, when all the money is spent, anyone will point to any transformative change in the country attributable to the legislation. Or whether, like the Obama stimulus, it will be completely forgettable, money strewn over the landscape without leaving much of a trace.

Shooting money out of a bazooka is not self-evidently what the state of America’s infrastructure calls for. But when the only tool you have is huge reconciliation spending bills, everything looks like a crisis urgently requiring more profligacy.

The bills are also a substitute for passing significant nonspending policy changes. Unlike FDR, Biden has narrow and tenuous congressional majorities. He’s not getting HR1, gun control, a higher minimum wage or immigration reform, and perhaps couldn’t even if Senate Democrats eliminated the filibuster.

What he can do, which FDR and LBJ never could, is reach for the word “trillion” as much as possible.