U.S. Sens. Bernie Sanders and John McCain arrive for the inauguration ceremonies at the Capitol. (Photo: Brian Snyder/Reuters)

Sen. Bernie Sanders released a video Friday morning lamenting that Donald Trump was preparing to be sworn in as the 45th president of the United States.

The former Democratic presidential candidate has been a longtime critic of Trump’s rhetoric and policies.

“Today is going to be a tough day for millions of Americans, including myself,” Sanders said. “But our response has got to be not to throw up our hands in despair, not to give up. But in fact to fight back as effectively and as vigorously as we can.”

According to the populist firebrand, Americans who oppose what Trump stands for need to keep their “eyes on the prize”: the continuing fight for a government that represents all Americans instead of just the ultra-wealthy.

“We’re going to go forward in the fight for economic, social, environmental and racial justice,” he continued. “That’s who we are. That’s what we’re going to do. We are not giving up.”

Just minutes earlier, Sanders praised the Obama family for representing the United States with “dignity, grace and civility” for the past eight years. Sanders was among the many political figures at the inauguration.

Former Democratic presidential candidate Hillary Clinton, who defeated Sanders for her party’s nod but ultimately lost the general election to Trump, also attended the inauguration with her husband, former President Bill Clinton. In a tweet, she explained that she was there to honor the nation’s democracy and “its enduring values.”

“I will never stop believing in our country & its future,” she wrote.

Throughout the campaign, both Sanders and Clinton repeatedly lambasted Trump for statements and policy proposals that they labeled regressive and rooted in bigotry.

Read more from Yahoo News: