Conservatives who want to overturn the controversial voluntary education standards known as Common Core have run into roadblocks in states across the country, largely erected by fellow Republicans who support the program.

In some states, measures requiring state boards of education to drop the math and English standards have advanced through committees. But in three Republican-controlled states — Arizona, North Dakota and South Dakota — Common Core repeals have lost critical votes in just the past two weeks.

The outlook for similar repeal measures in states like Mississippi, Kansas, New Hampshire, Arizona and Montana are grim as well.

“We feel very confident that we’re on the right track, that we’ve overcome most of the resistance” to Common Core, Idaho Gov. Butch Otter (R), a Common Core supporter, told reporters on Wednesday.

The Common Core standards, initially a program of the National Governors Association, have become a touchstone for conservative opponents who say the standards have become a tool for federal intervention in local education systems, after eleven states asked the Department of Education for permission to use federal grants to implement the standards. Few issues, including the Affordable Care Act, so outrage conservative activists.

“It comes down to two words: Barack Obama,” Mike Petrilli, president of the conservative Forham Institute and a Common Core supporter, said in explaining the opposition.

Legislators and governors in 45 states and the District of Columbia adopted the Common Core standards for math and English education. A 46th state, Minnesota, adopted only the English standard. As opposition mounted, legislators in a dozen states are undertaking reviews of the standards. But so far, only Oklahoma, Indiana and South Carolina have actually passed measures to drop out of Common Core.

(Supporters point out that Indiana’s new standards are virtually identical to Common Core, albeit under a different name, and that South Carolina remains a participant in the Common Core program until it develops alternative standards.)

Conservatives in more than a dozen states have introduced or plan to introduce measures dropping out of, or taking steps toward ending, Common Core. Those measures have made progress in a few states, but only one — in New Hampshire — has actually passed a state legislative chamber. That bill, which passed the state Senate this week, would prohibit the state’s Department of Education and Board of Education from implementing standards in local school districts.

The New Hampshire bill now heads to the state House, which Republicans control. But if it passes, it’s likely to be blocked by Gov. Maggie Hassan, a Democrat, who supports Common Core.

Bills in two other states have advanced through legislative committees. In Montana, a repeal has passed both the House Education and Appropriations Committees in the last week. It passed the full House on second reading, though a final vote on third reading is required to send it to the Senate.

In Arizona, the House Education Committee last week passed a repeal measure that would require new standards for English, math, science and American history.

But both bills face an uncertain future. As in New Hampshire, Montana’s legislature is entirely controlled by Republicans, but Democratic Gov. Steve Bullock is a Common Core supporter who could exercise his veto power. In Arizona, the governor isn’t the problem — Gov. Doug Ducey (R) opposes Common Core, a spokesman said — but the state Senate voted down a repeal bill earlier this week.

Mississippi’s state Senate voted earlier this week to establish a commission that would recommend a replacement for the Common Core standards. But opponents of Common Core voted present in protest of the bill, which only gives the commission the power to recommend, rather than require, alternative standards. An amendment to give the commission more power failed by a wide margin.

Common Core opponents still have the opportunity to repeal standards in states like Kansas or West Virginia, where bills await hearings before legislative panels. The Kansas House Education Committee heard testimony on its bill earlier this week, though the chairman has not called a vote.