WASHINGTON − Two years into his presidency, Donald Trump warned that he would "close the southern border entirely" if Democrats kept blocking funding for his proposed border wall.

It was the type of Trump rhetoric about the U.S.-Mexico border that Democrats regularly scorned as xenophobic.

But now, President Joe Biden is using similar language − seeking a border shutdown − as he urges Congress to pass a bipartisan bill under negotiation by senators to address what Biden has started to call "the border crisis."

Biden said the proposal would be the "toughest and fairest" set of border reforms in U.S. history and includes new presidential authority to "shut down the border when it becomes overwhelmed."

“If that bill were the law today, I’d shut down the border right now and fix it quickly," Biden said Saturday to Democrats in Columbia, South Carolina. 

Prep for the polls: See who is running for president and compare where they stand on key issues in our Voter Guide

Biden's push for a bipartisan border bill − one that also would include funding for Ukraine and Israel − marks a seismic shift to the right on border and immigration politics that has built over the past year.

Ahead of the 2024 presidential election, Biden is trying to strip Republicans of one of their most effective wedge issues, setting up a potential case that House Republicans − who have refused to back a bipartisan border bill − stood in the way of long-discussed action on the border.

Yet the discussions are a far cry from a comprehensive immigration bill Biden sent to Congress on his first day of office that sought to "restore humanity and American values to our immigration system" by offering pathways for citizenship to undocumented immigrants in the U.S.

"The discourse has become which of the parties can be harsher on border enforcement," said Melissa Gilman, co-director of the Immigration Clinic at the University of Texas, Austin, School of Law.

Gilman said the political posturing ignores the reality that the border has never been the subject of policies more stringent regarding screenings for entry, expedited removal of migrants and other areas.

"I have to think it's mostly because the Republicans have succeeded in creating a lot of fear around migration issues and have had success in doing that," Gilman said.

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The 2024 election calculus for Biden, Trump

For years, Republicans have rallied their conservative base and tried to appeal to independent voters by accusing the left of being soft on border enforcement.

Republicans are historically viewed more favorably on border security. A USA TODAY/Suffolk University Poll in October found more Americans, by a 50%-41% margin, trust Trump − the front-runner for the Republican nomination − to handle immigration over Biden.

Biden's tone has changed after record daily border crossings over the past year. The president has also heard from Democratic mayors who have raised concerns about needing additional resources to handle the influx of migrants in their cities.

"No, it's not," Biden said this month when a reporter asked him whether the border is secure. "I haven't believed that for the last 10 years, and I've said it for the last 10 years."

Republicans have taken cues from Texas Gov. Greg Abbott, whose hard-line tactics at the border – including installing razor wire along the Rio Grande – appear to be influencing the tenor of the national immigration debate.

Meanwhile, House Republicans are ratcheting up the border feud further by moving to impeach Homeland Security Secretary Alejandro Mayorkas, arguing he has refused to enforce the nation's immigration laws.

Although the text of bipartisan border legislation isn't finalized, senators have discussed giving the Department of Homeland Security power to shut the border down to migrants crossing illegally when daily crossings exceed a daily average of 4,000 over a one-week period.

And if migrant border encounters surpass an average of 5,00