U.S. President Joe Biden and former President Donald Trump are both headed to the U.S.-Mexico border this week, focusing immediate attention on the ongoing illegal migration of tens of thousands of people into the United States.

Illegal migration is a contentious issue that is certain to be a focus of debate in the November national election.

Biden and Trump have been sparring with each other over immigration rules from a distance at campaign rallies in different states, each blaming the other for the influx of migrants.

But on Thursday, they will be about 500 kilometers (311 miles) away from each other, with Biden headed to Brownsville, Texas, to meet with U.S. Border Patrol agents, law enforcement and local leaders and Trump headed to Eagle Pass, Texas, one of the most dominant migrant entry points.

Trump and Biden have each sought to stake claims that he is, or will be, the tougher chief executive on controlling migration over the new presidential term that starts next January.

FILE - A migrant child jumps to cross into the U.S. from Mexico through a gap in the border wall, in Lukeville, Arizona, Dec. 12, 2023.

FILE – A migrant child jumps to cross into the U.S. from Mexico through a gap in the border wall, in Lukeville, Arizona, Dec. 12, 2023.

Trump in his successful 2016 run for the presidency claimed he would build a border wall and make Mexico pay for it. Part of it was built during his presidency, but none of it was paid for by Mexico.

At one point, he sanctioned the separation of parents from their children as they tried to enter the U.S., but in the outcry that ensued he abandoned the effort.

In his successful 2020 campaign against Trump, Biden said he would adopt more humane migration policies, but now, with thousands of migrants arriving every week at the border, he has been forced to move toward tougher controls.

Biden said he would support a bipartisan proposal in the Senate for new immigration rules, but the legislation was doomed when Trump said it was not tough enough. Any Republicans who at first were inclined to support it quickly backed away from the measure, at Trump’s behest.

Now, Biden says he may sign an executive order on immigration, but an executive order does not have the same force of law as legislation approved by Congress and almost certainly would be challenged in lawsuits by pro-immigration groups.

At the same time, Republican House Speaker Mike Johnson, even though he helped defeat the bipartisan immigration plan, has demanded that migration controls be added to a spending bill Biden wants approved, which includes $60 billon in new aid for Ukraine’s fight against Russia’s two-year invasion.

Trump is close to securing the Republican presidential nomination for the third straight election cycle and has turned his attacks on Biden, with a recent Reuters/Ipsos poll showing immigration is the main concern for many voters and that Biden is vulnerable on the issue.

Meanwhile, House Republicans have impeached Homeland Security Secretary Alejandro Mayorkas, Biden’s immigration chief, claiming that he has left the border in chaos and ignored existing immigration restraints. With Democrats controlling the Senate, however, his conviction and removal from office are highly unlikely.

The fact that Biden is visiting the border on the same day as the former Republican president “shows just how big of a problem this is for him,” one Trump aide said.

A White House official said Biden in his Texas visit would reiterate calls for congressional Republicans to provide the funding needed for additional U.S. Border Patrol agents, more asylum officers, fentanyl detection technology and more.

Some information for this report came from Reuters.