Former U.S. representative Joe Walsh (R-Ill.) officially entered the Republican primary for the 2020 presidential nomination Sunday, making the conservative radio host the second candidate to challenge the president from his own party.

“I’m going to run for president,” Walsh announced on ABC News’ “This Week” with George Stephanopoulos. “I’m running because he’s [Trump’s] unfit; somebody needs to step up and there needs to be an alternative. The country is sick of this guy’s tantrum — he’s a child.”

The announcement, made while President Donald Trump is in France meeting with world leaders at the G7 summit, comes days after Walsh declared on CNN that he was “strongly, strongly considering” mounting a presidential challenge against Trump in the Republican primary.

Walsh said he plans to make a moral case against the president, targeting Trump’s character and arguing that the commander-in-chief is unfit to serve rather than focusing on the financial problems plaguing the country, as other potential candidates gearing up for a run have emphasized.

“He lies every time he opens his mouth,” Walsh repeated twice during his interview with ABC.

The conservative firebrand and Tea Party favorite joins former Massachusetts moderate Republican governor Bill Weld in the 2020 Republican primary. Weld ran for vice president on the libertarian ticket in 2016 with former New Mexico governor Gary Johnson, and announced his candidacy for president earlier this year.

Former South Carolina governor Mark Sanford, who lost a congressional primary as an incumbent representative in 2013 after Trump endorsed his challenger, has also said he is giving serious consideration to a presidential run from the Republican Party. Sanford said his candidacy would be aimed at restoring the Republican Party’s focus on fiscal issues and highlighting the nation’s growing debt and deficits, which have ballooned under the Trump administration.

“I’m a Republican. I think the Republican Party has lost its way on debt, spending, and financial matters,” Sanford told the Post and Courier last month. Sanford will be traveling to Iowa this week.

Prior to going into talk radio, Walsh served one term in Congress representing a suburban district of Chicago after winning an upset victory by 291 votes in the 2010 Tea Party wave in which Republicans took over control of the U.S. House of Representatives. Walsh later decisively lost the seat two years later in 2012 to Tammy Duckworth (D-Ill.), who is now a U.S. senator, losing by 10 percent.

Walsh admitted to supporting Trump in 2016, backing the president until Trump publicly denounced U.S. intelligence agencies at an international press conference in Helsinki, Finland in 2017.