Democrats are entertaining border policies once treated as complete non-starters, as pressure from a united GOP, angry Democratic city officials and desperate Ukrainians threatens to boil over into political disaster.

Why it matters: Republicans believe that if they can make 2024 the year of the border — an issue that polls consistently show is a top priority for voters and a vulnerability for Democrats — President Biden will be defeated at the ballot box in November.

Driving the news: As bipartisan Senate negotiations sputter over a deal to pair Ukraine aid with an immigration crackdown, House Speaker Mike Johnson (R-La.) led a delegation of 60 Republicans Wednesday to a border site in Eagle Pass, Texas.

• There, as cameras captured scenes of migrants attempting to cross the border just yards away, members of the GOP delegation threatened to shut down the government unless Biden "shuts down the border."
• One lawmaker recounted to Axios that a Houston-area sheriff told the group he'd support a government shutdown if it would ensure a more secure border.
• "House Republicans are once more compromising America's national security and economic growth with shutdown threats," White House spokesperson Andrew Bates said in response.

The House Homeland Security Committee also revealed Wednesday that it will formally begin impeachment proceedings against DHS Secretary Alejandro Mayorkas on Jan. 10.

• Texas Gov. Greg Abbott, meanwhile, continues to take matters into his own hands — busing tens of thousands of migrants to overwhelmed, Democratic-run cities and daring the administration to sue over his policies.
• And early reports indicate that border authorities processed more than 300,000 migrants in December — the highest monthly total on record.

Zoom out: A key turning point for Democrats came when major cities began sounding the alarm over their ability to serve thousands of newly arrived migrants.

• "Democrats have certainly shifted," Rep. Henry Cuellar (D-Texas), a key voice on immigration, told Axios. "It is mainly because they're now starting to feel and see what we in the border communities have been experiencing for so many years."
• "There's a more significant urgency to actually face this challenge," said Rep. Veronica Escobar (D-Texas), who also represents a border district.
• The migrant crisis has caused tensions to escalate between Biden and New York City Mayor Eric Adams, while other cities have also been demanding more federal support.
• "It's just inarguable that Greg Abbott has had no better ally than the mayor of New York," said one former Biden official, who admitted the situation in cities has forced some Democrats to change their tune.

In response, the administration has provided hundreds of millions of dollars in funding to cities and launched new clinics to expedite the work permit process for migrants there.

• "President Biden is committed to addressing this problem, that's why he submitted a supplemental funding request to Congress," said White House spokesperson Angelo Fernández Hernández.

The big picture: Biden has sought to embrace a tougher image and policies on the border, but the historic wave of crossings has still not slowed.

• He now faces an outdated, underfunded, backlogged immigration system at the mercy of a narrowly divided Congress in the middle of an election cycle.
• Biden's likely opponent, former President Trump, has relentlessly campaigned on the border crisis and used dehumanizing rhetoric about undocumented immigrants "poisoning the blood of our country."

State of play: The massive scale of migration forced the White House to ask Congress late last year for billions in emergency border security funds, a request that was paired with foreign aid for Ukraine and Israel.

• Republicans then used that as an opportunity to demand border policy changes in exchange for Ukraine aid — leading to the current Senate standstill.
• House Republicans, meanwhile, have suggested they will reject any deal that does not resemble the sweeping, hardline H.R. 2 immigration package they passed last May.

What they're saying: "While House Republicans have voted to cut border agents, the president has requested that Congress provide more agents and more resources to effectively manage and secure the border," White House press secretary Karine Jean-Pierre said Tuesday.

• "This is not about sending more money down here. It's about changing the policy, and the White House seems not to understand that," Johnson responded in an interview with CNN on Wednesday.

Between the lines: Former administration officials and Democrats acknowledge the growing political demand for Biden to get the border under control — or at least show he's taking it seriously, they tell Axios.

• Some are worried about how few Democratic immigration priorities — such as a pathway to citizenship for DACA recipients — seem to even be on the table in Senate negotiations.
• And some note the situation is a symptom of an issue Biden has had from the beginning: An administration and party that has struggled to articulate a cohesive stance on immigration — much less follow through.

Axios' Juliegrace Brufke contributed reporting.