Donald Trump speaks during a news conference at the at the Old Post Office Pavilion, soon to be a Trump International Hotel, in Washington on March 21. (Jabin Botsford/The Washington Post)

GOP front-runner Donald Trump, facing a likely setback in Tuesday's Wisconsin primary, plans to shift gears in the coming weeks, and give a series of policy speeches in settings more formal than the freewheeling rallies that have become his political signature.

Trump campaign manager Corey Lewandowski said in an interview Tuesday that a memo published by The Washington Post detailing how Trump plans to get Mexico to pay for his proposed border wall is a prelude to a series of moves that flesh out the policies that Trump has been speaking about in general terms in his rallies and in interviews.

Among the topics he will address are how to strengthen the nation's military, specific education reforms and the criteria by which a President Trump would select Supreme Court justices. The campaign hopes to stage those speeches in settings such as economic clubs in various cities and possibly the National Press Club in Washington, Lewandowski said.

Lewandowski insisted that the speeches do not represent a new strategy or course correction, but rather, "the natural maturation of the campaign."

President Obama said recent statements made by Republican presidential candidate Donald Trump about South Korea and Japan show he doesn't know much "about the world, generally." (Reuters)

Retired neurosurgeon Ben Carson, who endorsed Trump after abandoning his own presidential bid, said that he spoke with Trump by phone on Tuesday about a list of 10 to 12 judges from whom the billionaire might fill vacancies on the Supreme Court.

Trump plans to release the names in the coming weeks as a sign of his seriousness and a validation of his claims to being a conservative, Carson said.

"We now talk from time to time, including today, and we went over his list, which I think would be extraordinary," Carson added. "He's got his team studying these people very carefully."