Last week, Sanford said that he was focused on Hurricane Dorian and would wait until after the storm had passed to announce his decision on whether to seek the bid for the White House. Initially, Sanford said he would announce his plans by Labor Day, which was last Monday.
"I had planned to announce that back home this week," Sanford, 58, said in an interview on Fox News Sunday. "We had a hurricane come visit us on the coast of South Carolina so that sort of disrupted plans on that front. But I am here to tell you now, that I am going to get in."
In April, former Massachusetts Gov. Bill Weld officially entered the race, and last month, former Illinois Rep. Joe Walsh announced his candidacy.
Sanford told Chris Wallace that "I think we need to have a conversation on what it means to be a Republican." He said the GOP has lost its way on "a couple different fronts."
He later posted on Twitter: "I respect the view of many Republican friends who have suggested that I not run, but I simply counter that competition makes us stronger. "I believe competition of ideas is good, not bad, for the Republican Party and for our country."
In other tweets he explained why he is running for president.
"I am compelled to enter the Presidential Primary as a Republican for several reasons - the most important of which is to further and foster a national debate on our nation's debt, deficits and spending," Sanford wrote. We have a storm coming that we are neither talking about nor preparing for given that we, as a country, are more financially vulnerable than we have ever been since our Nation's start and the Civil War. We are on a collision course with financial reality. We need to act now."
Trump has wide support in his party.
On Saturday, the Republican Party in South Carolina voted to cancel their GOP primary for 2020. Kansas also voted Saturday to scrap the primary, and Nevada and Kansas are considering getting rid of primaries/caucuses.
Two days after Walsh announced his presidency, Trump posted on Twitter: "Can you believe it? I'm at 94% approval in the Republican Party, and have Three Stooges running against me. One is 'Mr. Appalachian Trail' who was actually in Argentina for bad reasons. Another is a one-time BAD Congressman from Illinois who lost in his second term by a landslide, then failed in radio. The third is a man who couldn't stand up straight while receiving an award. I should be able to take them!"
Sanford lost the primary in his congressional race last year after criticizing Trump, who endorsed Sanford's opponent, Republican Katie Arrington, hours before the polls closed and attacked him in a tweet for being "very unhelpful to me in my campaign to MAGA." Arrington later lost the election to Democrat Joe Cunningham.
Sanford served six years in his second stint in the U.S. House.
Sanford was first elected to Congress in 1994. Then, he ran successfully for governor in 2002 and was re-elected in 2006.
In June 2009, Sanford publicly revealed that he had engaged in an affair with María Belen Chapur after an unexplained disappearance in Argentina. He completed the term in 2010 despite censure from the South Carolina General Assembly.
He divorced from Jennifer Sullivan in 2010.
Sanford received a bachelor of arts degree in business from Furman University in 1983 and a master of business administration degree at the University of Virginia in 1988.