If Thune had decided to run for president, he would have been the third South Dakotan in the state's history to seek the country's highest office.
The most recent was Republican Larry Pressler, who entered the race in 1980. Democrat George McGovern ran in 1972. He won his party's nomination, and went on to be defeated by Richard Nixon.
Both Pressler and McGovern offered Thune congratulations on the decision, saying it was the right one for South Dakota. But Pressler says Thune could still achieve the presidency by being a good senator.
Larry Pressler's 1980 bid for president was unsuccessful, but he came away with some perspective about the process. He says John Thune would've had to clear several hurdles had he decided to run.
"A senator from a small state has a very hard time raising the money necessary to run a national campaign," Pressler said.
Pressler says Thune is a popular and successful senator, which sometimes can provide more political pull than a presidential candidacy.
"Gerry Ford never ran for president but he became president by doing a good job legislatively,” Pressler said. “So he can still achieve a cabinet post of the presidency or vice presidency but not running or running in the future."
Many are speculating that Thune is positioning himself as a vice-presidential candidate, but Pressler thinks it's just that; speculation. He says Thune has his priorities straight, and he proved that today.
"A lot of good senators don't spend all day thinking about being president or vice president; they should be thinking about doing a good job, and I think that's what John Thune is thinking about," Pressler said.
Thune’s fellow South Dakota delegates responded to the announcement.
"I respect John's decision not to run for President," Johnson said. "I look forward to continuing to work with John in the Senate on the difficult challenges facing South Dakota and the nation."
And Representative Kristi Noem said, "Senator Thune would have made an excellent presidential candidate and I would have enthusiastically supported his candidacy, but his decision is South Dakota's gain. I look forward to continuing in our work together representing South Dakota and fighting for more fiscal restraint in Washington. "