Just over a month into his presidency, President Biden is staring down a mounting crisis at the border that could be just as bad as the ones faced by Barack Obama and Donald Trump, if not worse.

Why it matters: Immigration is an issue that can consume a presidency. It's intensely and poisonously partisan. It's complicated. And the lives and welfare of vulnerable children hang in the balance.

The backstory: Biden came into office sounding a warmer, more welcoming policy that would treat migrants humanely. Desperate people have taken notice.

• And Biden reversed Trump’s COVID-era policy of turning away unaccompanied children — the very group that is now surging and being held for days in border stations unfit for children.

What's happening: Shelters are overflowing. Border crossings are rising. Border Patrol facilities are overwhelmed. And the new administration is taking fire from both the left and right as it grapples with the issue's harsh realities.

Where it stands: President Biden’s advisers told him this past week that the number of migrant children crossing the U.S. border without their parents this year is likely to far exceed the previous record.

• The federal government is taking custody of 321 migrant children per day, on average, and those numbers have been climbing rapidly all year.
• As reported by Axios earlier this week, federal officials said they need 20,000 beds to house an expected surge in migrant children crossing the border. They’ve already opened new facilities and plan to adjust some protocols to accommodate more kids while keeping everyone safe from the coronavirus.

What they’re saying: Progressives look at the rising number of migrant kids in temporary overflow facilities, including tents, and see a betrayal of Biden’s pledge to reverse Trump’s immigration policies. Some also say officials are too quick to invoke the pandemic to quickly deport adults and some families.

• Conservatives look at the crush of migrants and see the inevitable result of Biden ending too many Trump policies, including the practice of expelling unaccompanied children and canceling agreements that allowed the U.S. to send some asylum-seekers to Central America.

Between the lines: Families and children from Honduras, Guatemala and El Salvador often take the dangerous trip to the border to flee gang violence, natural disaster or severe poverty — only to arrive in a country that may not be equipped to quickly process and care for them.

• Officials have to balance both real humanitarian needs against their duty to enforce immigration laws — and most laws haven't changed in decades. The pandemic has only made things harder.
• Migration flows are difficult to predict, but systems and shelters at the border can't always adapt fast enough.

What to watch: There are still roughly three months left of what is usually the peak season for migrants coming to the U.S.-Mexico border. There is more that the Department of Health and Human Services can — and plans to — do to create space for more migrant children, but the projections are bleak.