Joe Biden’s presidency got off to a surprisingly hyperactive start. Trillion-dollar proposal followed trillion-dollar proposal and the 78-year-old Washington veteran who had promised normalcy on the campaign trail found himself being described as a “transformational” president. Commentators drew flattering comparisons with FDR and, presumably to much satisfaction in the White House, suggested that the Biden administration was already proving to be more consequential than Obama’s.

But after a superlative-laden first few months, the Biden train is losing steam. And the president knows it. “I hear all the folks on TV saying, ‘Why doesn’t Biden get it done,’” he vented this week. His own answer to the question: “Well, because Biden only has a majority of effectively four votes in the House and a tie in the Senate, with two members of the Senate who vote with my Republican friends.”

The current momentum-sapping impasse is an infrastructure package over which Biden cannot reach an agreement with Republicans — whose votes he needs if it is to be passed into law. The president has reduced the size of his infrastructure proposal from $1.7 trillion to $1 trillion, but is yet to strike a deal with Shelley Moore Capito, the West Virginian Senator and lead Republican negotiator.

For the left of the Democratic Party, such talks are nothing more than a hopeless, sentimental effort at bipartisanship: hundreds of millions of dollars worth of spending sacrificed at the altar of an old-timey Washington tradition that delivers zilch for their voters.

The real mirage isn’t bipartisanship. It’s the idea that Biden has a mandate — and the votes — for an era-defining legislative agenda

Leah Greenberg of the progressive group, Indivisible, typified that view in an interview with Politico this week: “Every day that passes where we’re still sort of hopelessly pursuing a mirage of bipartisanship is a day that we’re not moving on the priorities that Democrats were actually elected to do.”

But the real mirage isn’t bipartisanship. It’s the idea that Biden has a mandate — and the votes — for the kind of era-defining legislative agenda that Democrats, both inside the administration and on the Hill, have spent the last five months getting excited about.

Progressive Democrats like to think that were they to abolish the filibuster — the senate rule that means 60 votes are required to pass most new laws — it would be full speed ahead for an expansive liberal legislative agenda. But the Democrats’ difficulties are more than just procedural. The party’s grip on power in Washington is not nearly as tight as some seem to think and the enthusiasm that marked the start of the Biden presidency has not changed the reality of its internal divisions.

Biden and his party must come to terms with just how broad the coalition that elected him really is. It was a coalition made possible by Donald Trump: a wide portion of America’s political spectrum agreed on the importance of getting him out of power. But that glue is gone, as is the impetus that allowed Biden to pass a $1.9 trillion relief package shortly after taking office.

Now the president so recently described as transformational faces the prospect of priority after priority — from voting rights to immigration — hitting the legislative buffers. The busy first few months of the Biden years could prove to be the exception to an otherwise frustrated effort to get legislation through (so far, Biden’s only major legislative achievement is the American Rescue Plan). And the cause will not be Republican obstructionism but the fact that he doesn’t have the Democratic votes he needs.

This will anger and frustrate many on the left. But it would be a fairer reflection of what Biden was elected to do. Talk of a mandate for sweeping reform was always overblown given the narrow, Trump-focused, messaging of the campaign. The tight majority in the House of Representatives and a 50-50 Senate hardly suggests a country that has decided it is ready to overhaul its relationship with the federal government.

The danger for the president is that progressives refuse to accept this stalemate and, as frustration grows, the rhetoric ramps up, the tone sours and the already uneasy Biden coalition becomes unmanageable. If it does so, then Biden will surely grow to regret the tone that he and his allies struck in the first few months of his presidency, when an effort to generate some momentum behind his legislative agenda will instead look like an acute case of expectation mismanagement.