Mitt Romney has pledged that if elected president he will enact a voucher program that would allow parents of low-income and special needs students “to choose from any district or public charter school, or a private school where permitted by state law.” This position has become the norm for Republican presidential candidates — the party’s five preceding candidates also endorsed private school aid.

This was not the Republican position on education for most of the party’s history.

In 1875, Ulysses S. Grant, the second Republican president, called for a constitutional amendment that would mandate free public schools and prohibit the use of public money for sectarian schools. Grant attacked government support for schools run by religious organizations and called for the defense of public education “unmixed with sectarian, pagan or atheistical dogmas,” according to Mark Edward DeForrest, writing in the Harvard Journal of Law and Public Policy. At the time, the country was experiencing difficulties in assimilating immigrants, especially Catholics, and Republicans feared that religious schools would hinder acculturation of the newcomers.

Grant was not successful in securing a Constitutional amendment, but he inspired Congressman James G. Blaine, a Republican from Maine, to lead a movement to amend state constitutions to forbid direct government aid to religiously affiliated schools. As a result, 36 states adopted “Blaine amendments” according to Ira C. Lupu at George Washington University. In recent times, state courts often cited those constitutional provisions in striking down the latest legislation to aid private schools.

Republicans remained strong supporters of public schools and opponents of aid to private schools for nearly the next 100 years. Typical of the party’s position was this reference in the 1900 platform: “Enjoying the blessings of the American common school … [the American people’s] constantly increasing knowledge and skill have enabled them to finally enter the markets of the world.”

In 1960, when Richard Nixon ran as the Republican presidential candidate, he advocated for higher salaries for public school teachers and for a federal program to construct public schools. Not a word of support for private schools aid appeared in his position paper on education.

Nixon was defeated by John Kennedy, who proposed the civil rights bill that became law after his death and advanced the desegregation of the public schools. By the time Nixon ran again for president in 1968, many white ethnic voters in northern states were as unhappy with school integration as many white southern voters were. The 1968 Republican Party platform included a plank to “urge the states to present plans for federal assistance which would include state distribution of such aid to non-public school children…” Such a proposal would help to capture voters disaffected with civil rights laws.

In his first term as president, Nixon proposed tuition tax credits for parents whose children attended private schools, but the issue never came up for a vote in the Congress. When Nixon ran for reelection in 1972, he again endorsed this approach, noting in a radio address that “I am irrevocably committed to seeking tax credit legislation in the next Congress.” This position appealed to many southern white and northern ethnic voters, especially Catholics. But Congress refused to vote on his proposal.

The movement to aid private schools received a boost with the election of Ronald Reagan, who supported both tuition tax credits and private school vouchers. But on three separate occasions, Congress failed to approve Reagan’s private school aid bills. See Jeffry Henig, Rethinking School Choice, page 72. Interestingly, a near majority of Republican senators voted against tuition tax credits, showing that the party had not as yet fully abandoned its traditional support of public education.

Only within the last twenty years has aid to private schools become Republican orthodoxy. Today, a majority of Congressional Republicans vote regularly for tuition vouchers. At the state level, some Republican legislators still oppose vouchers, but the states that have adopted private school voucher programs (Wisconsin, Ohio, Florida and Indiana) did so at the urging of Republican governors and Republican legislative majorities.

This brief history illustrates how Republicans were motivated by political reasons to move away from their century-old position as strong advocates for public education and to become supporters of public funding for private schools. Beginning with Nixon, this strategy was a way to attract the votes of citizens who favored public aid for private schools because they opposed school integration.

Today, this tactic continues even as school desegregation has been downgraded as a priority by the Congress and federal courts, but the politics of Republican support for private schools has gained new elements. First, it is a way to fracture the Democratic coalition by appealing to African American voters who are dissatisfied with bad public schools and would like an opportunity to send their children to good private schools. As conservative strategist Grover Norquist told the Washington Times in 1998, “School choice reaches right into the heart of the Democratic coalition and takes people out of it.”

Cynically, politicians who take this tack disregard the facts that most proposed voucher programs do not provide enough government aid to pay for most of the costs of private education and that there are not enough private schools to absorb a major shift of students from public schools. Nor do they acknowledge the evidence from a decade’s worth of studies on publicly funded voucher programs. As noted in 2011 research synthesis by the Center on Education Policy, these studies generally show no clear advantage in academic achievement for students who attend private schools with publicly funded vouchers, compared with similar students in public schools.

Second, Republican advocacy for vouchers is a way to weaken the clout of the National Education Association and the American Federation of Teachers. Republicans are leery of these two major teacher unions because in electoral politics they mostly favor Democrats, the party that has shown greater support for public schools. As Terry Moe, a senior fellow at the conservative Hoover Institution, noted in a 2002 interview with the Heartland Institute, the teacher unions “have a lot of money for campaign contributions and for lobbying … They also have a lot of electoral clout because they have many activists out in the trenches in every political district.” Then, he got to the heart of it: “School choice allows children and money to leave the systems and that means there will be fewer public teacher jobs, lower union membership, and lower dues.”

So, all of the Republicans’ talk about giving parents the right to choose is a politically expedient strategy, regardless of whether voucher or tax credit supporters truly believe this policy is best for children. Just beneath the surface of the education rhetoric are political motivations to thwart integration, weaken the Democratic coalition, and cripple the teachers’ unions. Even traditional Republican support for assimilating through common public schools the increasing numbers of immigrants has been pushed aside for politics.

Keep that history in mind during this election season when you hear the voucher rhetoric and other oratory about the need to send public dollars to private and religious schools. Politics, not education, is at work here.