US president Donald Trump speaks to the media aboard Air Force One

Donald Trump has returned to Washington, DC, after an “amazing day” visiting the grieving communities of El Paso, Texas, and Dayton, Ohio, on a mission to heal divisions in the aftermath of the two devastating mass shootings that left 31 people dead over the weekend.

The president was met with boos from protesters upset by his racist rhetoric and undermined his own efforts to bring consolation by angrily tweeting about the “LameStream Media” and his political rivals and enemies in the press from Air Force One, even threatening to release a “racism list” to attack Democrats.

In Iowa, Democratic 2020 challenger Joe Biden accused him of “fanning the flames of white supremacy” - a sentiment later echoed by Elizabeth Warren - prompting Mr Trump to respond on Twitter: “Sooo Boring”.

On Wednesday alone, three White House hopefuls — Elizabeth Warren, Kirsten Gillibrand and Amy Klobuchar — offered sweeping proposals that touch on everything from farm subsidies to rural broadband and health care.

The trio of senators are among the parade of candidates who will fan out across Iowa this weekend to participate in the famed state fair and other events.

Trump protests: President visits Texas and Ohio after mass shootings Show all 31 1 /31 Trump protests: President visits Texas and Ohio after mass shootings Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators chant as they protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District AP Trump protests: President visits Texas and Ohio after mass shootings El Paso Trump headed to El Paso, after visiting Dayton, Ohio to offer a message of healing and unity, but he was met by hostility in both places by people who fault his own incendiary words as a contributing cause to the mass shootings AP Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre US President Donald Trump greets first responders as he visits El Paso Regional Communications Centre AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre An anti-Trump protestor holds a sign as police are lined up outside University Medical Centre Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso Demonstrators hold a sign as the motorcade carrying President Donald Trump departs a joint operations center after meeting with first responders after the El Paso mass shooting, Wednesday, Aug. 7, 2019, in El Paso, Texas. (AP Photo/Evan Vucci) Evan Vucci AP Trump protests: President visits Texas and Ohio after mass shootings El Paso Anti-Trump protesters hold a banner outside the makeshift memorial to the victims of the WalMart shooting that left a total of 22 people dead, in El Paso, Texas, on August 7, 2019. - President Donald Trump consoled victims of a mass shooting in Ohio on Wednesday but protesters and opponents denounced what they say is his extremist rhetoric on race and immigration. The president's trip to Dayton, where nine people were gunned down over the weekend, was to be followed immediately after by a stop in the border city of El Paso, Texas, where 22 were murdered. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators gather to protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District early Sunday morning, Wednesday, Aug. 7, 2019, in Dayton. Twenty-four-year-old Connor Betts opened fire in Dayton early Sunday, killing several people including his sister, before officers fatally shot him. (AP Photo/John Minchillo) John Minchillo AP Trump protests: President visits Texas and Ohio after mass shootings El Paso Democratic presidential candidate Beto ORourke hugs a woman at a makeshift memorial outside Walmart honoring victims of the mass shooting there which left 22 people dead. Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso Anti-Trump protesters hold signs outside the makeshift memorial to the victims of the WalMart shooting that left a total of 22 people dead, in El Paso, Texas, on August 7, 2019. - President Donald Trump consoled victims of a mass shooting in Ohio on Wednesday but protesters and opponents denounced what they say is his extremist rhetoric on race and immigration. The president's trip to Dayton, where nine people were gunned down over the weekend, was to be followed immediately after by a stop in the border city of El Paso, Texas, where 22 were murdered. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso Marisela Hernandez holds sign to protest the visit of President Donald Trump to the border city after the Aug. 3 mass shooting in El Paso, Texas, Wednesday, Aug. 7, 2019. Aiming to play the traditional role of healer during national tragedy, President Donald Trump paid visits Wednesday to cities reeling from the mass shootings. (AP Photo/Andres Leighton) Andres Leighton AP Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre An anti-Trump demonstrator holds up a placard outside the University Medical Center, where U.S. President Donald Trump holds a meeting with first responders in the wake of last weekend's mass shootings at a Walmart store, in El Paso, Texas, U.S., August 7, 2019. REUTERS/Jose Luis Gonzalez JOSE LUIS GONZALEZ Reuters Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre President Trump and First Lady Melania Trump greet PFC Glendon Oakley (second right), who saved several lives during the mass shooting in Texas AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators chant as they protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District early Sunday morning, Wednesday, Aug. 7, 2019, in Dayton. (AP Photo/John Minchillo) John Minchillo AP Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre An anti-Trump demonstrator holds up a placard as police block the area outside the University Medical Center, where U.S. President Donald Trump holds a meeting with first responders in the wake of last weekend's mass shootings at a Walmart store, in El Paso, Texas, U.S., August 7, 2019. REUTERS/Jose Luis Gonzalez JOSE LUIS GONZALEZ Reuters/Amanda Voisard Trump protests: President visits Texas and Ohio after mass shootings El Paso Beto ORourke consoles a man at the makeshift memorial outside Walmart Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso, University Medical Centre An anti-Trump demonstrator yells near police outside the University Medical Centre Reuters Trump protests: President visits Texas and Ohio after mass shootings El Paso TOPSHOT - El Paso residents protest against the visit of US President Donald Trump to the city after the Walmart shooting that left a total of 22 people dead, in El Paso, Texas, on August 7, 2019. - President Donald Trump consoled victims of a mass shooting in Ohio on Wednesday but protesters and opponents denounced what they say is his extremist rhetoric on race and immigration. The president's trip to Dayton, where nine people were gunned down over the weekend, was to be followed immediately after by a stop in the border city of El Paso, Texas, where 22 were murdered. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty Images Trump protests: President visits Texas and Ohio after mass shootings Dayton President Donald Trump and First Lady Melania Trump arrive at Wright-Patterson Air Force Base AP Trump protests: President visits Texas and Ohio after mass shootings El Paso Makeshift memorial for victims of the shooting that left a total of 22 people dead at the Cielo Vista Mall Walmart AFP/Getty Images Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators gather to protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District early Sunday morning, Wednesday, Aug. 7, 2019, in Dayton. (AP Photo/John Minchillo) John Minchillo AP Trump protests: President visits Texas and Ohio after mass shootings President Trump greets Dayton Mayor Nan Whaley as he arrives at Wright-Patterson Air Force Base AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators gather to protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District early Sunday morning, Wednesday, Aug. 7, 2019, in Dayton, Ohio. Twenty-four-year-old Connor Betts opened fire in Dayton early Sunday, killing several people including his sister, before officers fatally shot him. (AP Photo/John Minchillo) John Minchillo AP Trump protests: President visits Texas and Ohio after mass shootings Dayton Damon Smith presents a message to President Donald Trump beside a makeshift memorial in Dayton AP Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators gather in front of an inflatable "Baby Trump" to protest the presidents arrival AP Trump protests: President visits Texas and Ohio after mass shootings Miami Valley Hospital, Dayton Demonstrators gather to protest the arrival of President Donald Trump outside Miami Valley Hospital after a mass shooting that occurred in the Oregon District early Sunday morning, Wednesday, Aug. 7, 2019, in Dayton. President Donald Trump is headed to Dayton and El Paso, Texas on Wednesday to offer a message of healing and unity, but he will be met by unusual hostility in both places by people who fault his own incendiary words as a contributing cause to the mass shootings . (AP Photo/John Minchillo) John Minchillo AP Trump protests: President visits Texas and Ohio after mass shootings El Paso A photo of victim Javier Amir Rodriguez, a 15-year-old sophomore Getty Trump protests: President visits Texas and Ohio after mass shootings Dayton Demonstrators protest the visit of US President Donald Trump to the site of the mass shooting in Dayton, Ohio, on August 7, 2019. - Nine people were killed on August 4 in the city's popular Oregon District. (Photo by Megan JELINGER / AFP)MEGAN JELINGER/AFP/Getty Images MEGAN JELINGER AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso A message is left for Donald Trump AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso Signs and flags adorn the makeshift memorial for victims of the shooting that left a total of 22 people dead at the Cielo Vista Mall Walmart, in El Paso, Texas, on August 7, 2019. (Photo by Mark RALSTON / AFP)MARK RALSTON/AFP/Getty Images MARK RALSTON AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso People hug at the makeshift memorial AFP/Getty Trump protests: President visits Texas and Ohio after mass shootings El Paso People pray at the makeshift memorial AFP/Getty

The focus on rural Iowa is a mainstay of presidential politics, sending candidates on a sometimes-awkward pilgrimage to the far corners of the state that holds the first-in-the-nation caucuses.

But Democrats say the chase for the heartland is especially urgent this year as the party tries to win back some voters who supported Mr Trump in 2016.

A strong showing in Iowa, they say, could prove a candidate’s ability to make inroads in other rural communities across the country.

The challenge for Democrats is to rebuild the multiracial coalition across urban and rural areas that twice sent Barack Obama to the White House. His victory in the 2008 Iowa caucuses helped build momentum to claim the party’s presidential nomination. He later carried Iowa in the 2008 and 2012 general elections while also winning states with urban centers, such as Pennsylvania and Michigan.

In 2016, Mr Trump ate into that path , carrying Iowa, Pennsylvania, Michigan and Wisconsin.

Some Democratic candidates are working to reverse those gains by offering ambitious changes to rural voters. Ms Warren’s proposal on Wednesday would reshape the current farm subsidy system into a program that would break up big agribusinesses and guarantee farmers certain prices, which she said would raise farmers’ incomes and save taxpayer money.