Sen. Cindy Hyde-Smith speaks during a campaign event in Meridian, Mississippi, November 25, 2018. Jonathan Bachman | Reuters

Mississippi voters head to the polls Tuesday in the final Senate election of the 2018 midterms, a contest shaped by racial issues that will determine how wide the Republicans Senate majority will be in January. GOP Sen. Cindy Hyde-Smith hopes to fend off an upset from Democratic former Agriculture Secretary Mike Espy in the red state. Republicans aim to avoid their second shocker in the Deep South within the last year, after Democratic Sen. Doug Jones won a Senate special election in deep red Alabama in December. The winner of Tuesday's Senate special election runoff will serve the remainder of retired GOP Sen. Thad Cochran's term, which extends through 2020. Hyde-Smith was appointed to replace the ailing lawmaker earlier this year. But her remarks that evoked Mississippi's history of racist violence — and criticism that she did not properly explain or apologize for them — have made the contest in the conservative state more competitive than Republicans would like. President Donald Trump offered some last minute help to Hyde-Smith on Monday with rallies in Mississippi, a state he carried by about 18 percentage points in 2016. He defended the GOP senator for her comments that surfaced earlier this month about attending a "public hanging," which awakened memories of lynchings in the state and prompted numerous Hyde-Smith campaign donors to ask for a refund. Espy, who is black, has said her comments gave the state "another black eye that we don't need" and "rejuvenated old stereotypes." An Espy campaign ad that targets Hyde-Smith's comments also says that "we can't afford a senator who embarrasses us."

Senate candidate Mike Espy takes an interview with media during a news conference in Jackson, Mississippi, November 26, 2018. Seth Wenig | Reuters

During his stops in the state Monday, Trump told reporters that he knows "where [Hyde-Smith's] heart is, and her heart is good." He also noted that the senator apologized for her remarks. At a debate earlier this month, Hyde-Smith claimed the comment was "twisted," and she apologized to "anyone who was offended." But she has not answered repeated media questions about the remarks since. On Tuesday morning, Trump took to Twitter to again urge Mississippians to vote for Hyde-Smith. He has a serious interest in the GOP keeping the seat: A victory would give Republicans a 53-47 majority in the Senate, which would help him to confirm conservative judicial nominees and push for pieces of his economic agenda in Congress. Democrats will have control of the House in the next Congress, which will make it tougher for Trump to pursue his policy goals. Political experts in the state have said Espy likely needs Democrats to turn out in significantly larger numbers than Republicans to win. While Hyde-Smith's remarks may motivate Democrats, particularly the black voters who make up about a third of the state's electorate, Trump's visit may help to even the enthusiasm gap. Sixty percent of likely voters in Mississippi approve of the president, including 93 percent of Republican likely voters, according to an NBC News/Marist poll last month.