If Joe Biden wins the presidency, his biggest challenge in Washington might not be finding cooperation with Republicans — it could be satisfying the demands of members of his own party.  

Twice in recent days, reminders of the coming clash between moderate — or establishment — Democrats and the party’s younger, more assertive left wing sprung into public view. The warning shots came as the Democratic diaspora has mostly set aside significant disagreements left unsettled by the presidential primary season to focus on the more urgent task of wrestling the White House away from President Trump.

First, former President Barack Obama gave an interview to the popular “Pod Save America” and reminded the podcast’s mostly liberal audience that the progressive change many of them seek only happens if the Democratic Party controls all levers of executive and legislative power and that the party has to be open to compromise.   

“We have to accommodate for the fact that they’re going to be some regional differences and that’s OK. That’s part of the big tent and that’s part of the process that we move forward,” the former president said of his party.  

But on Friday, a cohort of liberal lawmakers and like-minded interest groups and labor unions — many of whom once openly clashed with Mr. Obama over domestic and foreign policy — sent a letter to Senate leaders signaling an absolutist stance on a key element of any new president’s early months: Filling top government positions.   

In the letter, the Democratic House lawmakers called on senators in both parties to oppose confirming “any nominee to an executive branch position who is currently or has been a lobbyist for any corporate client or c-suite officer for a private corporation, in this or any future administration.”  

Noting that both Democratic and Republican presidents have relied on corporate veterans to serve at the top levels of government, the progressives said, “we should stop trying to make unsupportable distinctions between which corporate affiliations are acceptable for government service and which are not. We should be honest about the fact that such distinctions are nothing more than partisanship dressed up in transparently false claims of necessity.”  

The letter was signed by long-serving members of the House Democratic Caucus’s liberal wing — Representatives Raul Grijalva, of Arizona; Jim McGovern, of Massachusetts; Barbara Lee, of California and Nydia Velasquez, of New York. But co-signers also included three members of “The Squad” — Representatives Alexandria Ocasio-Cortez, of New York; Rashida Tlaib, of Michigan; Ayanna Pressley, of Massachusetts — and other rising liberal stars, Representatives Pramila Jayapal, of Washington and Katie Porter, of California.  

That kind of absolutist stance is exactly the kind of move Mr. Obama warned against this week.  

In the podcast interview, Mr. Obama’s former speechwriter Jon Favreau asked, “What’s your advice to those people who want to see not only a more progressive Democratic Party, but more progressive policies enacted in Washington?”   

Look, I think that number one — win first, right? I think everybody’s kind of moved into that mindset,” Mr. Obama said. “You know, let’s get through the next three weeks and then the next three months and then let’s figure out what our internal debates are going to be.”  

“It is very important for progressives to continue to press their agenda, because there are going to be other forces that are pressing on the White House from the other direction,” he added.   

But the former president also urged restraint: “The caution I always have for progressives is making sure that as you push for the most you could get, that at a certain point you say: ‘All right. You know what? Let’s get this done and then let’s then move on to fight another day.'”  

He recalled disagreements with Democrats over passage of the Affordable Care Act, noting that it required a 60-vote supermajority in a divided Senate in order to pass.   

When moderate members of the Senate Democratic caucus — including then-Senators Joseph Lieberman, independent of Connecticut, and Ben Nelson, a Nebraska Democrat — refused to support a public option in the comprehensive health-care bill, he had to back off. And even though the Dodd-Frank bank reforms passed during his administration didn’t entirely eliminate Wall Street greed and malfeasance, he said the legislation put in place “guardrails” that kept the entire financial system from falling into financial shock.   

“So progressives, if you want progressive legislation, get out there and keep working after the president is elected,” he said.   

Several progressive groups are doing just that, especially some that openly fought the idea of a Biden presidency.   

In Iowa, former consultants to independent Vermont Senator Bernie Sanders are now drawing from their successful Iowa caucus playbook to whip up support for Biden.   

America’s Progressive Promise PAC, led by former Sanders senior aides Jeff Weaver and Chuck Rocha, and Nuestro PAC, an outfit targeting Latino liberal voters and established by Rocha, are teaming up to spend about $500,000 to target Iowa’s Latino voters with political mail and digital ads already airing in other more Latino-dominated states. The Sanders presidential campaign had spent millions of dollars targeting roughly 68,000 Latino registered voters in the state – a small, but significant bloc that helped Sanders eke out a popular vote win in the caucus.  

The digital ad targeting Iowa Latinos stars young former supporters of Sanders imploring fellow Democrats to vote for Biden. Several young people in the ad say, “I was for Bernie. But now, we’re all for Joe Biden. Because Biden’s endorsed by Bernie Sanders.” They note that Biden has a plan to fight student debt and supports significant changes in climate change policy.  

Another pro-Sanders group, Justice Democrats, also released a digital ad this week with a similar message: Biden isn’t perfect, but he isn’t Trump.   

An exhausted-looking mother seated in her backyard as her young child runs around tells the camera, “For six months, everything is COVID-this and COVID-that. I lost my f—ing job because we’re all trying to stay at home to get this under control. And our president does what? Are you f—ing kidding me? Look, maybe you don’t [like?] the other guy running for president. I get it — I don’t like anyone right now. But could you do me a favor? Take ten minutes this November and f—ing vote. Can you do that for me?”  

If this targeted outreach to liberal voters buoys Biden and helps him eke out wins in competitive battleground states like Arizona, Iowa and Nevada, progressives are going to expect something in return. It seems the push to ban corporate leaders from serving in government is just the start.   

“The revolving door needs to stop, not just change direction every few years,” the progressives wrote.  

Their letter wasn’t addressed directly to Biden or his White House transition team, which is beginning to lay the groundwork, mostly virtually, for a White House transition that could be delayed by prolonged ballot counts and legal challenges in several states, should he win the presidency.  

A spokesman for the Biden transition office didn’t have immediate comment on the lawmakers’ letter. But many of Biden’s fellow Democrats will be watching closely to see how he and his team respond.