Ben Carson, who is facing increasing scrutiny over his grasp of foreign policy, is traveling to Jordan on Friday to visit Syrian refugees, in order to gain an understanding of the pressing issue and to polish his candidacy.

“I find when you have firsthand knowledge of things as opposed to secondhand, it makes a much stronger impression,” Mr. Carson said in an interview before his departure, planned for late Thanksgiving Day on a charter aircraft.

In a surprise visit, he plans to go to the Azraq refugee camp in northern Jordan, where he will visit a clinic and a hospital. He is bringing soccer balls and Beanie Babies to distribute to children.

Mr. Carson, a retired neurosurgeon, was leading in some state and national polls before the Paris terror attacks, but his support has dropped with national security concerns looming larger in the Republican nominating race. In Iowa in particular, Donald J. Trump, who called for a registry of Muslims in America, has taken the lead in polls, and Senator Ted Cruz, who has harshly criticized President Obama over the rise of the Islamic State, has jumped into second place.