A commentary posted at The Wall Street Journal suggests President Donald Trump is being forced to turn back to the "pugilistic" immigration rhetoric he used during the 2016 presidential campaign because his core base of supporters is "eroding."

According to the Journal's Gerald Seib, Trump rode into the White House by emphasizing immigration, trade and infrastructure and the president's comments lately indicate he is falling back on what got him there as illustrated by his "sh*thole" comments about African nations and Haiti.

"After a year focused more on tax cuts, health care and deregulation—issues that tend to appeal more to traditional Republicans—the focus so far this year has moved decisively back to standard Trump issues," Seib wrote.

According to the commentator, Trump's fallback on more extremist red meat issues may be part of a plan to rally voters the president hopes will support Republicans in the 2018 midterm election -- thereby assuring him he won't face a hostile Democratic-majority Congress.

Seib notes that Trump's support is plummeting after one year in office, with poll numbers showing a precipitous collapse specifically among the people who voted for him in 2016.

"A dive into Wall Street Journal/NBC News polling suggests that, after Mr. Trump’s tumultuous first year in office, the president’s support among his staunchest proponents has eroded some, though still is pretty solid," Seib wrote. "Among whites without a college degree—a core Trump support group—approval of the job he is doing as president slipped to 55 percent in December from 59 percent in February. Disapproval has risen to 41 percent from 32 percent."

"Similarly, the share of whites without a college degree who have a negative image of Mr. Trump personally has risen to 40 percent from 33 percent," he added.

"A return to the signature Trump issues would seem to be a way to end and perhaps reverse that erosion at the base," he explained although he admitted that Trump's promise to build a wall between the United States and Mexico seems to only appeal to the most hardcore Trump voters -- with only 31 percent putting it at the top of their list.

"Of course, much of Mr. Trump’s campaign appeal was based not on specific policy positions, but more on his pugilistic attitude—and the simple fact he wasn’t Hillary Clinton, an object of hatred for many Trump voters," Seib conceded. "More than four in 10 Trump voters said making sure she didn’t become president was the top reason they voted for him."

Regardless, the commentator added, Trump is "expending a lot of capital and earning a lot of enmity at home and abroad on immigration and building a wall, subjects not as central for his supporters as commonly supposed."

You can read the whole editorial here.