Many Republicans are hoping for financial support from President Trump, whose fund-raising power in the party remains unmatched despite his low poll numbers.

© Meridith Kohut for The New York Times

Robert F. Kennedy Jr., then a prominent anti-vaccine activist, preempted the 2019 visit with a letter to the Samoan prime minister requesting to study the Pacific island nation's measles, mumps and rubella vaccines after the deaths of two children who had received them. In the letter, he used the words vaccine or vaccination eight times.

President Donald Trump's trade war with Canada is escalating as the midterm elections approach, threatening Republican efforts to address voters' economic concerns in a year when control of the U.S. Senate hinges on states along the border between the United States and its northern neighbor.

The two-week runoff window since the two Republicans were the top vote-getters in an Aug. 11 primary has been a slugfest.

South Carolina Republicans will return to the polls Tuesday for the fourth time since June to replace the late U.S. Sen. Lindsey Graham on the fall general election ballot.