Sen. John ThuneJohn Randolph ThuneGOP leaders to Trump: Leave Mueller alone Toyota halts self-driving car tests on public roads Senate Commerce presses Facebook, Cambridge Analytica for answers on data MORE (R-S.D.) on Thursday said he is not ruling out a run for president in 2016.

“I don’t think you ever rule anything out in politics if you want to make a difference,” he said during an interview with Real Clear Politics

Thune made the comments while championing a piece of legislation he introduced earlier this year with Sen. Tim Kaine (D-Va.) that would require budgets and major pieces of legislation to be accompanied by an analysis of the long-term impacts of those proposals. 

“I am passionate about [the Inform Act] and I hope that we have other people who run for national office who are as well,” he said. 

Thune said there are a number of Republicans who have already started to hint at a White House run. He said he hopes anyone who does would support his legislation. 

“We’ve got a lot of good people that are starting to make moves in that direction,” he said. “I do think it doesn’t matter who our nominee is, who the Democrat nominee is. I hope [the Inform Act is] embraced by both sides.”

The Republican Conference chairman was considered a potential candidate for president in 2012 before announcing, early in the process, that he would not run. He was also seen as a potential vice presidential running mate to Mitt Romney before Romney ultimately chose Rep. Paul Ryan (R-Wis.).

Earlier this year, Thune said he had no plans on running for president. His answer was prompted in February by an elementary schoolchild who asked whether he would run. 

"Do I plan on running for president?” Thune asked. “I don't. I enjoy the job I have. And being the president is a very, very hard job."

In 2011, he decided against a run because he feared he would not be able to raise enough money to compete and did not want to let his Senate duties lag. 

Thune has been left out of most early polling for the 2016 nomination as a host of young Republican senators have dominated presidential speculation, particularly Sens. Rand Paul (Ky.), Ted Cruz (Texas), and Mario Rubio (Fla.).

Thune was first elected in 2004 when he beat out then-Senate Democratic Leader Tom Daschle (S.D.). He's up for reelection in 2016.