Sen. Rand Paul (R-Ky.) fired a warning shot on education at Jeb Bush (R) Tuesday evening, saying the former Florida governor's support for Common Core education standards would be a "big problem" for him among conservatives in a Republican primary.

"I think most conservative Republicans think that education should be more at the local and state level. So yeah, I think it will be a big problem," Paul told The Washington Post in a brief interview in the Capitol.

Bush announced Tuesday morning that he has decided to "actively explore" a run for the presidency. Paul may also run. The senator's reaction to Bush's news: "I think the more the merrier."

"I think we've got a big party," he continued. "I think we have people from all different wings of the party."

Bush has been an outspoken supporter of Common Core, which is basically a national set of education standards in math and English most states have adopted.

Many conservatives, including Paul, oppose it. Even some previous Common Core champions have turned against it.

Bush offered a nuanced defense of Common Core last month, with advice for those who want a different set of standards.

“There is no question we need higher academic standards and — at the local level — diverse, high-quality content and curricula,” he said in a Washington speech. “And in my view, the rigor of the Common Core State Standards must be the new minimum in classrooms. For those states choosing a path other than Common Core, I say this: Aim even bolder...raise standards and ask more of our students and the system.”