A majority of Americans support building a wall along the U.S.-Mexico border for the first time since Donald Trump popularized the idea during his 2016 presidential bid, according to a Monmouth University poll.

The 53% of Americans who now approve of a border wall is a significant increase from the highest level, 44%, of support it received during the years Trump was in the White House, according to the poll, released Monday.

The newly registered support for the border wall comes as both President Joe Biden and Trump are set to make separate trips to the U.S.-Mexico border in Texas on Thursday.

The poll found that concern about illegal immigration is growing, with 61% citing it as a serious problem. Some 91% of Republicans said it is a serious problem, up from 66% in 2015, according to the poll. Democrats were also more likely to cite it as a major issue: 41% now compared to 33% nine years ago.

“Illegal immigration has taken center stage as a defining issue this presidential election year. Other Monmouth polling found this to be Biden’s weakest policy area, including among his fellow Democrats,” Patrick Murray, director of the independent Monmouth University Polling Institute, said in a statement.

The Monmouth University poll of 902 U.S. adults was conducted by phone Feb. 8-12. It has a margin of error of plus-or-minus 4.1%.