Arkansas and other Southern states have emerged as critical battlegrounds in state and local officials’ efforts to persuade enough unvaccinated Americans to get Covid-19 shots in order to halt a nationwide surge in coronavirus infections. Arkansas now has the country’s second-highest rate of new daily Covid-19 cases, trailing only Louisiana.

The surge’s highly contagious Delta variant has been especially devastating to states in the South and Midwest, including Florida, Alabama, Mississippi, Louisiana, and Missouri, as well as Arkansas. Except for Florida, all of those states have full vaccination rates that are significantly lower than the national average of 58 percent of eligible people.

President Biden announced a vaccine mandate for all federal employees on Thursday and urged state governors to start offering $100 payments to patients who receive vaccine doses as an incentive to help boost the U.S. vaccination rate, which fell short of the administration’s goal of having 70 percent of American adults at least partially vaccinated by July 4.

Vaccination rates in Arkansas increased rapidly earlier this year but then “flatlined” in early April, according to Col. Rob Ator, a retired Air National Guard commander appointed by Republican Gov. Asa Hutchinson to lead the state’s vaccination effort. Mr. Hutchinson has been touring the state in recent weeks to promote vaccinations. Arkansas’s full vaccination rate for residents age 12 and up is 42.5%.

Most people who were eager to get the vaccines did, according to Col. Ator, who added that he is now focusing on the “movable middle”: the roughly 30% of Arkansans who he says are undecided about the vaccine or are waiting for more information, including seeing friends and family members safely immunized.

Arkansas has spent $6 million on vaccination advertisements in traditional media outlets and on social media, primarily targeting residents of small towns and rural areas, as well as young people who, according to Col. Ator, consider themselves “bulletproof” against serious Covid-19 cases. The average age of hospitalized patients has decreased by 12 years since the emergence of the Delta variant, Col. Ator said.

To spread the word, public-health officials are collaborating with churches, local business groups, and historically Black fraternities and sororities.

It’s possible that the effort is paying off. Vaccine demand in Arkansas has increased 54 percent in the last two weeks, according to Col. Ator. According to state health officials, on July 22, the state broke its one-day record for vaccine doses administered by 3,000, with 14,000 shots administered across the state.

Mayor George McGill of Fort Smith, Arkansas, the state’s second-largest city with a population of nearly 90,000, has spent the majority of his weekly radio show over the last month urging residents to get vaccinated. According to a Wall Street Journal analysis of federal data, demand for the vaccine in Sebastian County, where the city is located, peaked in May.

The city has increased its spending on billboards, radio and television commercials. According to the Journal’s analysis, the county’s first-dose vaccination rate increased by 6 percentage points in July, from 30% to 36%, after increasing by only 1.8 percentage points in June. On Tuesday, 159 people came to a vaccine clinic in a nearby mall for their first shots.

Misinformation, apathy, and politics are driving vaccine resistance, according to public health experts and state officials. Attendees booed Mr. Hutchinson and heckled state epidemiologist Jennifer Dillaha at a recent town hall meeting in Mountain Home, an Ozark Mountain tourist town in Baxter County, after both said there is no evidence the vaccines cause fertility problems.

According to the Centers for Disease Control and Prevention, Baxter County has the highest seven-day average rate of new daily cases in the state, at 104 per 100,000 people, as well as one of the highest rates of new Covid-19 deaths.

Mississippi officials this month urged all residents 65 and older, regardless of vaccine status, to avoid large indoor gatherings. In response to an increase in Covid-19 cases, Mayor Quinton Lucas of Kansas City, Mo., announced on Wednesday that the city would reinstate its mask mandate beginning Aug. 2. St. Louis implemented a mask mandate on Monday, which was quickly challenged by the St. Louis County Council.