MILWAUKEE — The Democratic primary race began as a clash of ideas. But when the Democratic National Convention convened on Monday, the party assembled with a singular aim: defeating President Trump.
From the progressive left to the moderate wing, Mr. Trump has served for months as the glue keeping the party from fracturing. And never has this détente been more obvious than in the wide-ranging lineup for the first night of the convention, when, in the name of unity, the virtual stage was open not just to Democrats of various persuasions but to Republicans as well.
The festivities were set to convey one message from the Democrats. Whatever their ideological differences with one another or the Democratic nominee Joseph R. Biden Jr., ousting Mr. Trump was the primary concern.
The appeal would come from political leaders including John Kasich, a onetime Republican candidate for president, and also from Michelle Obama, the former first lady; from Senator Bernie Sanders, the progressive standard-bearer, and also Democratic moderates including Senator Doug Jones of Alabama, Gov. Andrew M. Cuomo of New York and Gov. Gretchen Whitmer of Michigan.
Taken together, the spectacle was to be a fitting coda to a primary season defined by the notion of electability. More than policy or identity, it had been this all-consuming desire to beat Mr. Trump that cut across ideological and generational lines. The global pandemic and Mr. Trump’s handling of it has only intensified the resolve.
“That bigger picture of what’s at stake here for the country is so dominant today,” said Representative Pramila Jayapal of Washington, who endorsed Mr. Sanders in the primary but is now firmly behind Mr. Biden.
“Look at what could happen to this country if Donald Trump gets elected for another four years — we will lose America,” she added. “There is no question in my mind that the result would be just horrific and we will lose our democracy.”
The Democrats’ unified front is a striking departure from four years ago, when Sanders supporters booed and jeered at Hillary Clinton, then the party’s nominee. Days before the convention, the release of stolen D.N.C. emails revealing that party officials had been eager to help Mrs. Clinton and undercut Mr. Sanders confirmed longstanding complaints of bias from the Vermont senator and threatened to plunge the proceedings into chaos.
But if the convention is intended to rally Democrats with a common resolve, it is also a reflection of an essential quality of Mr. Biden’s, harking back to his days in the Senate: He strives to build bipartisan consensus and believes compromise across political divides is possible. Since winning the primary, he has stamped this political worldview onto the party’s DNA. The result is a convention that is more an extended infomercial built to persuade the skeptical moderate than a rousing show of defiance meant to fire up the party’s base.
There are still serious reservations about Mr. Biden among progressives, who have already signaled that they intend to push Mr. Biden should he be elected, on issues including health care, climate change, education and criminal justice. Some have refused to back the Democratic Party platform because it does not support “Medicare for all,” a symbolic move that nevertheless suggests conflict to come.
For now, those ideological fights could wait.
With the convention transformed into an entirely virtual production, and the unpredictability of a live event replaced with a highly orchestrated digital affair, the party’s unity message on its first night was on plain display: The theme, for anyone in doubt, was “We the People.”
Among the most anticipated speakers of the night was Mr. Sanders, once again at a convention as a runner-up. But the context is far different than it was four years ago, when his sustained attacks on Mrs. Clinton helped foment deep divisions between his wing of the party and establishment Democrats that burst out into the open on the convention floor.
During his 2020 presidential bid, however, he made clear that beating Mr. Trump was a top priority, placing it on a par with his calls for progressive policies like “Medicare for all” and tuition-free public college. In the interest of unity, he vowed to support the eventual nominee if it wasn’t him.
Mrs. Obama will deliver the final speech of the night, four years after her mantra of decency, “When they go low, we go high,” became a guiding principle for Democrats as they battled Mr. Trump. To many Democrats, the former first lady is a reminder of what once was — before a global pandemic, before an economic crisis, before a reckoning over racism and, above all, before Mr. Trump.
The cross-ideological unity was a dramatic shift from the intraparty fights during the presidential primary that often centered on progressive litmus tests. Mr. Sanders and Mr. Biden may now speak about each other warmly, but during the primary campaign they most clearly embodied opposing ends of the Democratic spectrum on health care policy, breaking up big technology companies, raising taxes on corporations and supporting the expansive climate legislation known as the Green New Deal.
In some ways, the message of the first night’s lineup was more indicative of the 2018 midterm elections, during which moderate victories existed alongside progressive gains, and the Democratic Party swept to power with a big-tent message of holding Mr. Trump’s administration accountable.
Mondaire Jones, a lawyer who won the Democratic primary in New York’s 17th Congressional District and is most likely headed to Capitol Hill in the fall, said both can be true: There is reason for progressives to feel good about Mr. Biden and to be ready to push his administration.
“There is cause for optimism,” he said, adding that there were also areas where Mr. Biden and his running mate, Senator Kamala Harris of California, “are lagging behind American public opinion, in areas like ‘Medicare for all.’ And both of them will have the most progressive Congress in the history of the United States to pressure them and hold them accountable.”
Matt Bennett, co-founder of the center-left political group Third Way, said it was vital for Democrats to give Mr. Biden space to make overt appeals to conservative and moderate voters.
“Anytime you’re expanding the size of the tent, that’s helpful,” Mr. Bennett said. “There are not a lot of persuadable voters late, but to the extent there are any, you have to give them permission to do what they know is right.”
The inclusion of several conservative voices was the most explicit attempt at this persuasion. In a section of the night called “We the People Putting Country Over Party,” the largest set of speakers of the evening, several Republicans and Democratic moderates planned to make a case for Mr. Biden in terms more personal than political.
Mr. Biden has, in recent polling, exploded to an early lead against Mr. Trump behind a unique coalition that includes seniors who have soured on Mr. Trump after his handling of the coronavirus pandemic, college-educated moderates in suburbs, and white voters without a college degree. A portion of the programming was laser targeted at those constituencies.
The night was set to showcase not just Mr. Biden’s pitch for November, but also the themes that have grounded his political career. A longtime senator from Delaware, he was known for his relationships with both Republicans and Democrats, and leaned on those personal histories to pass legislation throughout his career.
His political history has not come without criticism, and Mr. Biden continues to be accused by more liberal members of his party of caring more about Washington traditionalism than ideals like social justice and equality. Indeed, it was the thrust of the attack that Ms. Harris lobbed at him during their first presidential debate.
It remains a sticking point. Representative Alexandria Ocasio-Cortez, a leader of the progressive wing of the party who will speak at the convention Tuesday, tweeted her displeasure at Mr. Kasich’s speaking slot, considering his anti-abortion views.
“It’s great that Kasich has woken up and realized the importance of supporting a Biden-Harris ticket. I hope he gets through to GOP voters,” Ms. Ocasio-Cortez said. “Yet also, something tells me a Republican who fights against women’s rights doesn’t get to say who is or isn’t representative of the Dem party.”
With a different nominee, in a different time, such pressure from the left wing of the party might worry Mr. Biden’s campaign. But this is Mr. Biden, consensus builder at heart. And the opponent is Mr. Trump, the great Democratic uniter.
Cori Bush, the progressive St. Louis activist who recently won her Democratic primary and is most likely headed to Congress next year, said the priorities for Democrats were driven by their constituents: “The people in our community want Donald Trump out.”