Since Donald Trump's shocking primary and general election victories in 2016, arguably the biggest long-term question confronting political analysts has been what the events of that year portended for the era that began with Ronald Reagan's defeat of Jimmy Carter in 1980. Would Trump end the Reaganite dispensation by fully transforming the GOP into a worker's party? Or would he fail, opening up the possibility of a future Democratic president liberating himself and his party from the constraints Reagan placed on them decades in the past?

Four years later, we are much closer to knowing the answer.

For a few short weeks after Trump's defeat of Hillary Clinton, I wondered if Trump might just pull it off. Trump was a real-estate developer, after all. What if he came out of the gate in January 2017 with a bold infrastructure plan, combining his promise of a big, beautiful border wall with a proposal to spend trillions of dollars on vast public-sector building projects around the country — roads, bridges, trains, nuclear power plant construction, electrical grid revamps, and more? If he combined this with a turn against immigration, combativeness on trade, and follow-through on campaign vows to defend the welfare state and expand health-care coverage — Trump just might succeed in pivoting sharply away from Reaganite orthodoxy and peeling off crucial working-class support from the Democratic Party.

But of course this isn't what happened. "Infrastructure Week" became a four-year-long running joke, as the administration repeatedly gestured toward producing and pushing a plan and ended up choking every time. Instead, we got the usual Reagan-era obsession with tax cuts, a failed attempt to repeal the Affordable Care Act (with no replacement anywhere in sight), and constant culture war trolling by the president on Twitter and at campaign-style rallies before throngs of adoring supporters. And incompetence and scandals and impeachments and a shambolic response to the worst pandemic in a century.

Now it's the other party's turn.

If the opening months of the Biden administration are any indication, the Democrats seem far more eager and prepared to seize the opportunity to define the end of the Reagan era and shape the one to come. We can see this most clearly in the sweeping infrastructure plan the Biden White House released this week. It proposes a dramatic shift for American politics — potentially the biggest lurch to the left since FDR succeeded in passing the New Deal in the wake of Herbert Hoover's presidency.

Those saying it's more accurate to call Biden's "American Jobs Plan" the biggest liberal initiative since Lyndon Johnson's Great Society have a point. But that framing fails to account for the relevant political context. The Great Society's ambition was broadly consistent with Democratic Party priorities throughout its mid-century dominance. FDR's agenda continued and expanded under Harry Truman. It remained largely static under Dwight Eisenhower and JFK but wasn't in any significant way reversed. Johnson then expanded it further but didn't change direction in a fundamental way.

What Biden is attempting now is something very different — a major leftward change of orientation from the preceding 40 years. That kind of swing hasn't happened since 1933.

What Eisenhower was to the decades following FDR's paradigm-shifting presidency, Bill Clinton was to the Reagan era: a placeholder who largely kept the broad contours of prevailing assumptions in place and mainly did the work of reconciling his own party to the new reality. After an early failure to successfully chart a more progressive course with health-care reform (an effort that sparked a backlash severe enough to hand unified control of Congress over to Republicans for the first time in 42 years), Clinton shaped and signed tough crime and welfare reform bills, both of which built primarily on neoconservative ideas. Then he consolidated Reaganite premises by proclaiming that "the era of Big Government is over" in his 1996 State of the Union. Clinton's greatest achievement in his second term was achieving a modest budget surplus.

Barack Obama pushed further, but his efforts were modest compared with what we're seeing now. The stimulus package passed during the Great Recession was roughly $800 billion. Today it's conventional wisdom to consider that much too small and to blame the country's very slow path back to full employment over the next decade on that supposedly paltry figure. But at the time, it was the most Obama could accomplish politically (it passed Congress with just three Republican votes in the Senate and none in the House). Then Obama put all of his legislative eggs in the basket of crafting and passing the Affordable Care Act, which was a significant new government program with progressive aims. Its cost? At the time of passage, the Congressional Budget Office estimated its net cost at $788 billion over 10 years.

The furious Republican opposition to ObamaCare was about far more than its price tag. It was also a function of the GOP's rejection of a major new expansion of government into the health-care industry and the prospect of people losing insurance coverage they liked. All of it confirmed that the ACA was a very big initiative, large enough to convince some that it would mark a break from the Reagan era's constraints on progressive policymaking.

But it didn't happen. Instead, the backlash against ObamaCare was strong enough to produce, in the 2010 midterm election, the biggest shift of seats in the House of Representatives since 1948, 62 years in the past.

The Reagan era wasn't over yet.

But is it now?

A Republican president and a bipartisan coalition in Congress passed roughly $3 trillion in pandemic relief during 2020. A few weeks later, in Feb. 2021, the new Democratic president and his party in Congress passed another $1.9 trillion in spending that combined additional pandemic relief with a range of programs that go well beyond the immediate COVID-19 crisis and could well become permanent. That's approximately $5 trillion in emergency spending in less than a year.

And now, less than three weeks after Biden signed the COVID-19 relief package, his administration has proposed an infrastructure plan that would cost something on the order of $2.3 trillion over the next 10 years. The "American Jobs Plan" is about far more than improving the nation's roads, bridges, trains, and electrical grid. It's also the opening bid of an ambitious policy initiative on climate. It proposes $400 billion for elder care (including higher wages for those who work in that sector). It contains money for broadband internet and affordable housing and public school upgrades and community college expansion and R&D investments and supply-chain upgrades and what appears to be the rudiments of an industrial policy in the manufacturing sector and much, much else besides.

Bill Clinton and Barack Obama never came close to attempting anything on such a scale.

What are Republicans proposing as an alternative, beyond grumbling about opposing the plan because it raises taxes? A memo released earlier this week by Rep. Jim Banks of Indiana talks about Trump's remarkable success at delivering the working class into the arms of the GOP and insists that the party needs to keep it there. But how? The ideas amount to little more than fighting Biden on immigration, continuing to insist on tough-minded trade policies, and talking a lot about the culture war, including a commitment to mocking the Democrats for their elitism.

Read during the same week that Biden proposed a multi-trillion-dollar infrastructure plan filled with public-works projects that would benefit large swaths of the American economy, the memo reads like a document of a party thinking small and simply hoping for a happy accident.

If Joe Biden and his party can pass the "American Jobs Plan" in anything close to its proposed form and then weather the 2022 midterm election without losses to rival those they suffered in 1994 and 2010, they will have accomplished something the previous two Democratic administrations thoroughly failed to do — which is to bring the Reagan era in American politics to a definitive end and begin the essential work of defining its successor.