Mark Sanford
Mark SanfordReuters

Former South Carolina Governor Mark Sanford announced on Sunday he will launch a primary challenge for the 2020 Republican nomination.

"I had planned to announce that back home this week. We had a hurricane come visit us on the coast of South Carolina so that sort of disrupted plans on that front," Sanford told Fox News Sunday. "But I am here to tell you now, that I am going to get in."

Asked why he was running, Sanford replied he was running because "I think we need to have a conversation on what it means to be a Republican," adding that he thinks the Republican Party has lost its way on "a couple different fronts."

Sanford, discussing what was then a potential candidacy, told CNN in July there has been "no discussion of debt, deficit and government spending in Washington these days," and that those issues would be a focal point of his campaign were he to run.

However, although Sanford has been a frequent critic of Trump, he has said he would back the President instead of a Democrat.

With his announcement, Sanford became the third Republican who has announced he will challenge Trump.

Former Massachusetts Gov. Bill Weld officially announced in April that he would be entering the race for president in 2020.

In late August, former Illinois Rep. Joe Walsh also announced he would challenge Trump.

"I'm running because he'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," said Walsh.

All three candidates face an uphill battle in the efforts to take down Trump, as history shows that presidents generally only face serious primary challenges when their approval rating within their own party is at 75% or below.