Joe Biden will deliver his first speech to a joint session of Congress on Wednesday evening and will pass the 100-day mark of his presidency two days later. Which means his presidency is just getting started.

But that hasn't kept pundits from pronouncing on its place in history, with the emerging consensus being that the Biden administration is shaping up to be transformational. That's certainly the view of Jonathan Chait, who just published an article in New York that claims Biden's first hundred days have already "reshaped America." I made my own contribution to the genre of prematurely sweeping takes with a column earlier this month proposing that Biden had the potential to bring the post-Reagan era of American politics to an end with a progressive agenda more ambitious than any we'd seen since the New Deal nearly 90 years in the past.

I still think that's true, though the key word in that last sentence is potential. There's no denying that Biden and his party have a lot they want to accomplish — certainly far more than any Democratic president has considered possible since before Ronald Reagan's election in 1980. But the key question — really the only one that matters in the final analysis — is whether they can actually get it, or anything like it, enacted. Unless and until they do, pronouncing Biden a transformational president makes as much sense as awarding Barack Obama the Nobel Peace Prize less than a year into his presidency.

So far, Biden has one big accomplishment under his belt. He got a massive (nearly $2 trillion) pandemic relief package passed. That was a big deal, especially since it got enacted just a few weeks after the previous Congress passed a $900 billion relief package, which was itself just nine months removed from the original $2.2 trillion CARES Act. By any measure, $5 trillion in federal relief in under a year (especially without any significant offsetting revenue enhancements) is huge, and certainly seems to be a sign that Congress is newly willing to spend in a way that it hasn't been inclined to for a very long time.

Yet this early success for the new administration doesn't tell us very much about the viability of Biden's subsequent proposals. These include an infrastructure package that costs more than $2 trillion and actually covers lots of things (like elder care, an industrial policy, and investment in green technologies) that only a professional spinmeister for the Democrats (or a die-hard partisan on Twitter) could describe with a straight face as "infrastructure." Biden's also about to announce another large proposal (this one costing $1.8 trillion) that will include a modest tax hike on income at the upper levels and a more substantial increase on investment income (capital gains) along with substantial new spending on child care, pre-kindergarten, paid family leave, free community college, and extra money for the Affordable Care Act's health-care exchanges.

That's a lot.

Now, if Biden can get all of this, or even a substantial portion of it, through Congress over the next several months, then he will indeed have accomplished what I laid out in my earlier column, expanding leftward the bounds of the possible in Washington and moving definitively beyond the constraint that have limited progressive policymaking for the past four decades.

But this remains a very big if.

The left will point to various structural impediments to Democrats getting their way — while also taking potshots at Sens. Joe Manchin (D-W.Va.) and Kyrsten Sinema (D-Ariz.) for refusing to eliminate the legislative filibuster in the Senate — and there is some truth to their complaints. But not nearly as much as they like to suppose. The fact is that the country remains deeply divided, with the left facing a wall of opposition from the right, and vice versa, no matter which party controls the White House and the two houses of Congress.

Biden may be showing FDR-levels of ambition, but he lacks anything resembling FDR levels of public support. Biden won the presidency with 306 Electoral Votes and 51.3 percent of the popular vote. FDR won in 1932 with 472 Electoral votes and 57.4 percent of the popular vote. Biden's party controls Congress, but by the narrowest possible margins. FDR came into office with Democrats holding a 313-117 majority in the House and a 58-37 majority in the Senate. Four years later, he won re-election with 523 Electoral Votes and 60.8 percent of the popular vote, while his Democratic majorities in the House and Senate swelled to 334 and 74, respectively.

It's obviously far too early to know whether Biden and his party might be able to increase their support going into 2022 and 2024, but the chance of them reaching anything close to those margins in our era of partisan polarization is vanishingly slight. Biden's 54 percent approval rating is quite a bit higher than his uniquely unpopular predecessor ever enjoyed, but it's also fairly low in historical terms for the early months of a new administration (significantly lower than what Barack Obama enjoyed and in a range similar to that of Bill Clinton and George W. Bush) and also remarkably stable.

That leaves Biden and his party stuck somewhere just slightly above 50 percent support in the country as a whole — which is a much better showing than Republicans have managed recently, but hardly enough to blow up the status quo in the nation's capital and redraw the lines of political combat. It also leaves the president's ambitious, big-ticket agenda in limbo, along with other major progressive initiatives, including H.R. 1 (the omnibus bill dealing with voting rights and related issues), the PRO Act (a big priority for organized labor), statehood for the District of Columbia and Puerto Rico, and immigration reform.

Given these constraints, Biden is doing the only thing he can, which is to try and ram through as much as possible with his bare-minimum majorities. He's doing so in the hopes that those accomplishments will prove popular and give Democrats wins in 2022 that make even more policy triumphs possible in the run-up to a re-election bid two years later. If he succeeds, Biden may yet come to be known for inaugurating a new era of ascendant progressivism.

But 100 days in, that looks like an awfully big if.