WASHINGTON, D.C. - President Joe Biden announced he is ending his presidential re-election campaign Sunday.

In a letter he sent out, he said he believes "it is in the best interest of my party and the country for me to stand down and focus solely on fulfilling my duties as President for the remainder of my term."

Biden also endorsed Vice President Kamala Harris as the next nominee for the Democratic Party.

Speaker of the House Mike Johnson, R - Benton, issued a statement saying if "Joe Biden is not fit to run for President, he is not fit to serve as President" and that he "must resign the office immediately."

Louisiana U.S. Senator Bill Cassidy said that "this decision is overdue." He also said that Biden has "thrown the country, the economy, and the Democratic party into total disarray" over the past two years, which Cassidy said was the timeframe that "President Biden’s mental capacity has been declining."

Louisiana Congresswoman Julia Letlow also issued the following statement:

“Even though President Biden will not be running, whoever the Democrats nominate will continue his Administration’s failed policies. Make no mistake, inflation will be persistent, the open border will continue to flood communities across Louisiana with fentanyl and other deadly drugs, domestic energy production will continue to be under a relentless regulatory attack, and our hardworking farmers will continue to have to deal with burdensome rules and requirements that threaten to put them out of business. The answer is clear: elect President Trump and Senator Vance to the White House and ensure Republican majorities in both houses of Congress.”

Watch ABC News' special report on the president's decision:

Read the full letter here: