President Donald Trump ridiculed Sen. Mitt Romney on Monday after the Utah Republican joined a march to the White House in solidarity with Black Lives Matter.

“Tremendous sincerity, what a guy. Hard to believe, with this kind of political talent, his numbers would ‘tank’ so badly in Utah!” Trump wrote on Twitter, sharing video of Romney marching with a group of Christians to the White House.

“We need a voice against racism; we need many voices against racism and against brutality. And we need to stand up and say black lives matter,” Romney said on Sunday as he marched.

Romney’s approval is underwater with Republicans, as only 46 percent signaled support for the Utah Senator in a Deseret News/Hinckley Institute of Politics poll conducted in May. Forty-nine percent of Republicans disapproved of his job performance, months after he joined Democrats to vote to impeach President Donald Trump.

Democrats give Romney a 60 percent approval rating, helping him reach a 52 percent approval rate overall.