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       U.S. President Joe Biden has kept pugilists from pillorying members of their own party, reassuring the left, while assuaging the moderates.

       JONATHAN ERNST/Reuters

       For months, American political figures and commentators have looked to the right to see the spectacle of a party in turmoil, struggling to define its mission and to tamp down fissures and stanch the strife among factions. All that time they should have been looking to the left as well.

       While the Republicans have stolen the attention for one of their colourful but consequential periodical battles for the soul of the GOP, the Democrats have been struggling to maintain harmony in their own camp, a fragile coalition of groups united principally in their contempt for Donald J. Trump.

       This was the week when the crevices separating the Democrats became visible and – to the distress of the party and to the danger of the presidency of Joe Biden – widened.

       This was the week when an establishment Democrat battled a progressive Democrat for the party nomination in a special by-election in central Ohio; when a progressive rebellion occurred over Mr. Biden’s delay in extending a COVID-prompted moratorium on eviction orders for renters amid a spike in Delta variant virus cases; when left-leaning lawmakers expressed impatience with party members willing and in some cases eager to accommodate Republicans on a massive infrastructure bill; and when new tensions developed around Democratic Senator Kyrsten Sinema of Arizona, accused of Neville Chamberlain-style appeasement of Republicans.

       For six months, Mr. Biden has kept pugilists from pillorying members of their own party, reassuring the left (on climate change and the wealth gap) while assuaging the moderates (on an overhaul of the Supreme Court and in his soothing rhetoric and benign profile).

       He has been especially effective in winning the loyalty of Senator Bernie Sanders, the Democratic socialist from Vermont and his principal rival in the 2020 presidential election, and Representative Alexandria Ocasio-Cortez, the progressive from New York. But in recent days Mr. Sanders’s protégé was defeated in the Ohio primary; a progressive Missouri Democrat, Representative Cori Bush, staged an extraordinary sit-in at the Capitol to protest the lapse in the eviction moratorium; and Ms. Ocasio-Cortez issued a blistering criticism of Ms. Sinema for her participation in bipartisan talks that produced a compromise infrastructure bill.

       “Good luck tanking your own party’s investment on childcare, climate action, and infrastructure while [excluding] members of color from negotiations and calling that a ‘bipartisan accomplishment,’ ” Ms. Ocasio-Cortez wrote in a tweet directed at the Arizonan, who is one of two party members standing in the way of Democrats’ efforts to eliminate the filibuster that requires 60 lawmakers’ approval to take up most Senate bills.

       All political parties have fissures and factions, and the Democrats have had their share even while holding the White House. Woodrow Wilson purged Democrats who were disloyal to his administration in the First World War years; Southern conservatives did not embrace many aspects of Franklin Roosevelt’s New Deal in the 1930s; Democrats who once had chosen Lyndon B. Johnson as their Senate majority leader recoiled at his prosecution of the Vietnam War in the 1960s; and distaste for the style and substance of Jimmy Carter led to the unusual challenge against a sitting president mounted by Senator Edward M. Kennedy of Massachusetts in the 1970s.

       Mr. Biden emerged as the 2020 Democratic nominee in large measure because he was acceptable to most elements of a party desperate to deny Mr. Trump a second term.

       “It was always in the cards that there would be a rebellion on the Democratic left,” veteran Democratic pollster Peter D. Hart said. “And it was always a certainty that the left would rise up and work for its priorities while Biden governed from the centre.”

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       Mr. Biden eventually patched things up this week, at least for the moment, by extending protections against tenant evictions and extending US$47-billion in rental assistance. He did so by intervening, perhaps with little legal basis, in an arcane dispute involving the Centers for Disease Control and Prevention’s designation of COVID transmission rates, a requirement for the implementation of the tenant protections.

       Mr. Sanders, the leading figure among progressives, turns 80 years old next month, but many of the rebels in the party are young. Ms. Ocasio-Cortez is 31 and members of the left-leaning group in the House of Representatives often referred to as the “Squad” have an average age of about 40 while the average age of the House is about 60.

       The tensions among Democrats are not confined to the national level.

       On the state level, it was New York state’s first Black and female attorney-general, the Democrat Letitia James, who produced the searing harassment report that endangered the tenure of Democratic Governor Andrew Cuomo, the ultimate Empire State establishment figure whose family accounts for nearly 23 of the past 38 years in the governor’s mansion in Albany.

       On the local level, a Pittsburgh-area group called the Allegheny County Independent Democratic Committee is taking on members of the area Democratic establishment in an effort, in its words, to “break the machine” and to emphasize, among other matters, LGBTQ, labour and racial justice issues.

       In the third decade of the 21st century, both parties have veered from the “big-tent” philosophy of American political parties that governor Ronald Reagan enunciated in a landmark 1967 speech in Long Beach, Calif., when he argued before a Republican group that “there is room in our tent for many views,” adding that “the divergence of views is one of our strengths.”

       Then again, nine years later, Mr. Reagan challenged sitting president Gerald R. Ford for the 1976 Republican presidential nomination. He lost that bid, but by January, 1981, would become president himself – and would successfully construct a “big tent” of his own that controlled the White House for 20 of the following 28 years.

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