More than a third of Americans now say they are worried “a great deal” about race relations in the US, which is higher than at any time since 2001, a new poll has found. The percentage of respondents who are worried a great deal rose seven points to 35 percent in the past year and has more than doubled in the past two years, according to a Gallup poll released Monday. Concern about race relations has risen during an 18-month period marked by a series of deaths of unarmed African Americans at the hands of police officers. These deaths sparked major, sometimes violent, protests and fueled the nationwide rise of the “Black Lives Matter” movement, which campaigns against violence toward black people. Prior to 2015, race relations were much less of a concern to Americans, relative to other national issues. “The rising concern about race relations as the nation's first black president completes his last year in office is a retreat from the optimism that swept the country in the immediate aftermath of President Barack Obama's first election win in 2008,” Gallup said. Race relations may not worry as many Americans as do issues such as the economy, affordable healthcare or crime, but Gallup's polling clearly shows that racial tensions over the past few years have significantly affected public opinion. A Gallup poll one night after Obama won the US presidency found that 70 percent of Americans believed racial relations would improve because of his victory. Republican strategists are already claiming that history will conclude that Obama’s presidency worsened race relations. In the current presidential election cycle, both Republicans and Democrats have attacked Republican presidential frontrunner Donald Trump for his campaign's racist overtones. Trump’s campaign has been defined by controversy from the beginning, including disparaging remarks about non-European immigrants and Muslims.