Immigration is about to roar back as a major crisis for President Biden: Republicans are already testing harsh new border messages for the coming midterm ad war.

Driving the news: This week's reports — that the administration plans to end the use of a COVID-19 immigration ban called Title 42 by May 23 — put a timeline on a scenario for which Homeland Security officials have spent months preparing.

• Axios recently scooped details of officials' internal deliberations about how to manage a hypothetical "mass migration event" in the coming weeks or months.
• The end of Title 42 and the movements that could trigger is what they were talking about.

The big picture: Democrats already were worried about losing suburban voters and centrist Hispanic voters over inflation and culture wars. A new border surge may only exacerbate those concerns while inflaming national security considerations.

• The White House has been in triage mode as it responds to Russia's invasion of Ukraine, a Supreme Court nomination, rising inflation, culture wars and multi-state challenges to voting rights and abortion rights.
• That all comes while it tries to salvage elements of Biden's Build Back Better plan stuck in a 50-50 Senate.

What we're hearing: The GOP senses opportunity and has pounced on immigration as an election issue.

• The Republican National Committee on Wednesday rolled out part one of a new video series focused on the border, which it calls "Unchecked."

What they're saying: "You would think there would be some concern about the politics of this," Sen. John Cornyn (R-Texas) told Axios. "I think this is a disaster for the administration and for Democrats generally."

• Some Democrats are raising concerns, as well. Sen. Mark Kelly (D-Ariz.) says he’s worried the administration doesn’t have a plan in place to deal with the fallout and prematurely ending the program could result in a humanitarian crisis.
• Sen. Mark Warner (D-Va.) said he thought it would be a "huge mistake" to do something that "might invite doubling, tripling, quadrupling of the numbers at the border."
• Sen. Joe Manchin (D-W.Va.) also told reporters Thursday he's opposed to ending Title 42, saying: "Just watch the news y'all put out every day, what’s coming across.”

There's also support from many Democrats to end Title 42.

• For example, Sen. Bob Menendez (D-N.J.), chair of the Senate Foreign Relations Committee, said the policy "is not the answer to whatever immigration crisis there is."
• If ending Title 42 leads to a new border crisis, he said, Democrats need a new law to deal with it — not keep leaning on the public health order.

Between the lines: Immigration has been a no-win situation for Biden.

Republicans blame his relaxation of hardline Trump-era policies for inviting new waves of undocumented immigration.

Progressives criticize the administration for not doing more to help undocumented immigrants and asylum seekers.

• Some congressional Democrats have held press conferences and sent letters calling for the end of Title 42.
• On the other hand, Democratic border-area representatives like Henry Cuellar and Vicente Gonzalez of Texas joined forces with Republicans on Tuesday.
• They petitioned the departments of Homeland Security and Health and Human Services to keep Title 42 until the government is better prepared and stronger measures are in place to address a border surge.
• Kelly and his fellow Arizona Democrat, Sen. Kyrsten Sinema, also recently warned Biden to keep Title 42 in place until agencies are ready.

How we got here: Title 42's use, begun under Trump and continued under Biden, has allowed officials to automatically turn back asylum seekers because of the COVID-19 emergency.

• Court challenges and the virus' transition from pandemic to endemic set the clock ticking on rescinding it.
• While many progressives and immigration activists have long criticized the policy as inhumane, argued it was illegal and sought its end, it's proved a useful tool in managing surges of undocumented immigrants to the southern border.
• Without it, officials predict surges up to a potential 18,000 people a day.

The bottom line: Immigration is bound to play a bigger role in some midterm races than others.

• But it could also fuel broader attacks from the right alleging that Biden is being weak and not controlling the border.

Editor's note: Axios' Hans Nichols and Sophia Cai contributed reporting to this story.