Pervasive partisanship and rapid-fire social media echo chambers have exacerbated our tendency to jump to conclusions, Axios managing editor Kim Hart writes.

• We see that in about everything from Joe Biden's behavior, to a student's viral encounter with a Native American man at a rally, to the Mueller report.
• Why it matters: Making assumptions is an age-old human flaw. But it is being worsened by the challenges of responding to an increasingly complex world at warp speed.

Viral internet: Everyone has encountered a too-good-to-be-true story on social media, whether it's viral outrage or viral feel-good.

• Research shows the social media ecosystem can lead to snap judgments, even based on incomplete information, to reinforce emotional identities and ideological positions.

One of the latest examples played out this week when Stephanie Carter, an entrepreneur and wife of former Defense Secretary Ash Carter, explained a 2015 photo showing Joe Biden standing behind her with his hands on her shoulders.

• Assumptions about the circumstances behind the photo went so viral that Carter wrote a Medium post to set the record straight and "reclaim" her story "from strangers, Twitter, the pundits and the late-night hosts."
• The real story, she wrote, is that while her husband was giving remarks after his swearing in, Biden "leaned in to tell me 'thank you for letting him do this' and kept his hands on my shoulders as a means of offering his support."

Other examples show how easily narratives catch fire online based on incidents that most of us didn't see firsthand:

• Covington Catholic students: Media outlets, celebrities and social media jumped on a viral videotaped encounter between a Native American man and high school boys, before more complete footage emerged.
• Sen. Dianne Feinstein on the Green New Deal: In a shortened clip, she appeared dismissive of young activists' concerns. A longer video shows dialogue that includes her offering an internship to one of them.
• The Mueller report: Big victory for President Trump, if you're a Republican. Or a colossal letdown, if you're a Democrat. The one thing both sides have in common: Neither has seen the report.

This reality can be empowering for marginalized voices speaking out on injustices such as #MeToo and #BlackLivesMatter.

• But it can also lead to disproportionate levels of punishment in an ecosystem that promotes the most outrageous content.

The cautious view among most Republican lawmakers and White House aides is that President Trump won’t follow through with his dramatic threat to close ports of entry at the border, Jonathan Swan reports.

• A source who has been talking to Trump about the border situation throughout the past week said that the president remains skittish about doing anything to disrupt the markets.
• Trump is encouraged by what Mexico is doing to apprehend migrants on their journey to the U.S.

"It’s the markets," the source said. "Closing the border, the markets would plummet."

• "He’s very well aware that there’s a commercial trucking component that would be devastating on Mexico and would be hurtful to the United States."

Be smart: As with everything Trump ... What is true at 10 p.m. on Wednesday could be false by 7 a.m. on Thursday, depending on who Trump talks to, what he watches, and what kind of mood he’s in.

We're told Joe Biden, his team and his family felt upbeat after the release yesterday of his Twitter video, which lacks an apology but promises changes:

• "Folks, in the coming month, I expect to be talking to you about a whole lot of issues, and I’ll always be direct with you."
• "Social norms are changing. I understand that, and I’ve heard what these women are saying. Politics to me has always been about making connections, but I will be more mindful about respecting personal space in the future."

See the video, read the statement.

Creeping floodwaters threaten Washington's cherry blossoms, AP's Ashraf Khalil writes:

• Decades of wear and tear from foot traffic, combined with rising sea levels and a deteriorating sea wall, have created a chronic flooding problem in the Tidal Basin.
• Twice a day at high tide, a large stretch of sidewalk next to the Jefferson Memorial is submerged by the rising waters.
• Teresa Durkin, senior project director of the Trust for the National Mall, said the higher silt concentration of the floodwaters is shortening the life span of the hundreds of cherry blossom trees that ring the basin.

The whole area needs refurbishing:

• The original 1880s design of the Tidal Basin wasn't equipped to handle the kinds of crowds and traffic the area now receives.

Some Mueller investigators have told associates that their findings were more troubling for President Trump than Attorney General William Barr has indicated, the N.Y. Times reports.

• Although details couldn't be learned, the report "is believed to examine Mr. Trump’s efforts to thwart the investigation."
• Why it matters: "This is the first evidence of tension between Barr and the special counsel's office."

One person told the WashPost: "It was much more acute than Barr suggested."

 "Even as Biden's fate is litigated," former TIME editor Nancy Gibbs writes in the magazine's new issue, "the larger tests facing Democratic candidates come into focus":

• "There is the challenge of the generational divide, in which a rising cohort, characterized by its diversity and tolerance, is intolerant of conduct that was long commonplace."

Why it matters: "The challenge to the 2020 candidates is addressing a nation sick of the paralyzing polarization."

• "There’s a reason most candidates are choosing to talk about Trump as little as possible, and frame a positive message on their own terms."

"Scientists Thought They Had Measles Cornered. They Were Wrong," the N.Y. Times' Donald G. McNeil Jr. writes.

• What's new: "A series of fierce, sometimes connected measles outbreaks — in places as diverse as Indonesia, the Philippines, Madagascar and Venezuela — ... have shaken global health officials."
• Why it matters: The outbreaks reveal persistent shortcomings in the world’s vaccination efforts, and threaten to tarnish what had been a signature public health achievement.

"Each year, state lawmakers across the U.S. introduce thousands of bills dreamed up and written by corporations, industry groups and think tanks," USA Today's Rob O’Dell and Nick Penzenstadler write after a two-year investigation.

• Why it matters: "Disguised as the work of lawmakers, these so-called 'model' bills get copied from one state Capitol to the next, quietly advancing the agenda of the people who write them."

"USA Today and The Arizona Republic examined nearly 1 million bills using a computer algorithm developed to detect similarities in language."

• "That search — powered by the equivalent of 150 computers that ran non-stop for months — found that at least 10,000 bills almost entirely copied from models were introduced nationwide in the past eight years."
• "More than 2,100 were signed into law."

Read the story. ... See a graphic.

Heather Higginbottom, a former top Obama administration official, will join the JPMorgan Chase corporate responsibility team in May to lead a new global public policy effort, CEO Jamie Dimon announces in his annual shareholders letter.

• "We believe the best way to scale programs that we have seen work in cities, states and countries around the globe is to develop actionable public policies that allow more people to benefit from economic growth," Dimon writes.

Higginbottom, most recently COO of CARE USA, was deputy secretary of state, deputy director of the White House Office of Management and Budget and deputy director of the White House Domestic Policy Council.

• Go deeper.

"Warner Bros. on Wednesday morning released the trailer for Joker, starring Joaquin Phoenix as the titular character in a standalone origin story about one of Batman's most iconic enemies," BuzzFeed News' Michael Blackmon writes.

• "The Martin Scorsese influence in the teaser is unmistakable," The Hollywood Reporter's Richard Newby notes. "Scorsese, who was once set to executive produce the film, is as equally an important reference point for Joker as the comics themselves."

"There’s level of serious silliness in Phoenix’s portrayal, and the majestic squalor of Gotham that makes Joker seem distinct from other comic book movies, musical even in its theatrical sense of reality that undoubtedly stems from the perspective of its central character."

• "But there’s a fear, not entirely unwarranted, that such a centralized perspective and unbroken look inside of the mind of one of comic’s most enigmatic villains will break the character."

Watch the trailer.