More than five years after U.S. governors began a bipartisan effort to set new standards in American schools, the Common Core initiative has morphed into a political tempest fueling division among Republicans.

The U.S. Chamber of Commerce leads establishment voices — such as possible presidential contender Jeb Bush — who hail the standards as a way to improve student performance and, over the long term, competitiveness of American workers.

Many archconservatives — tea party heroes Rand Paul and Ted Cruz among them — decry the system as a top-down takeover of local schools. The standards were developed and are being implemented by states, though Common Core opponents argue that President Barack Obama’s administration has encouraged adoption of the standards by various parameters it set for states applying to get lucrative federal education grants.

Tea party-aligned officials and candidates want to delay the standards or abandon them altogether in at least a dozen of the 45 states that adopted some part of the guidelines. Indiana lawmakers approved a repeal that now awaits a decision from Gov. Mike Pence.

“Common Core is like Obamacare: They passed it before they knew what was in it,” said William Evers, a Hoover Institute research fellow and lead author of a California Republican Party resolution denouncing Common Core.

To a lesser extent, Democrats must deal with some teachers — their unions hold strong influence within the party — who are upset about implementation details. But it’s the internal GOP debate that’s on display in statehouses, across 2014 campaigns and among 2016 presidential contenders.