Then-President-elect Donald Trump listens as Betsy DeVos, his pick to be education secretary, speaks at a “USA Thank You Tour 2016″ event in Grand Rapids, Mich., on Dec. 9. (Jabin Botsford/The Washington Post)

Despite thousands of phone calls, a pizza delivery and two Republican defections, the Senate has confirmed Betsy DeVos for as education secretary by a 51-50 vote. For the first time in U.S. history, a vice president cast the tiebreaking vote to confirm a Cabinet nominee. Still, the rocky confirmation suggests difficulty ahead for President Trump’s campaign promises on student vouchers. If we look closely at the confirmation votes — and the reasons behind them — we find a serious roadblock to Trump’s education agenda.

Why did two Republican senators vote against DeVos?

The two Republican defectors, Sens. Susan Collins (Maine) and Lisa Murkowski (Alaska), opposed DeVos in part because she advocates school vouchers as alternatives to public education. Despite DeVos’s assurance that she would not condition federal funding to the states on the adoption of vouchers, these two Republican senators were willing to break with their party over this issue.

In voting against DeVos, Collins and Murkowski are remaining true to their long-standing positions on vouchers. In July 2015, both voted against student vouchers, three times. Here’s the background.

The National Education Association, one of the largest teacher’s unions in the country, releases a list of legislative votes that touch on teachers’ interests after every congressional session. From this, the NEA grades House and Senate members’ advocacy. For the 114th Congress (2015-16), the NEA listed three amendments touching on the use of federal funding for student vouchers: S. Amdt. 2139, S. Amdt. 2110 and S. Amdt. 2132.

Education Secretary Betsy DeVos on Feb. 8 told Education Department staff that her "confirmation process and the drama it engendered has been a bit of a bear." (The Washington Post)

Female Republican politicians may break with their parties on “family” issues

As expected, no Democratic senator voted for any of these pro-voucher amendments. But 14 Republicans opposed at least one of the three amendments: Sens. Collins, Murkowski, Lamar Alexander (Tenn.), Kelly Ayotte (N.H.), Roy Blunt (Mo.), Shelley Moore Capito (W.Va.), Thad Cochran (Miss.), Bob Corker (Tenn.), Deb Fischer (Neb.), Orrin G. Hatch (Utah), Dean Heller (Nevada), Mark Kirk (Ill.), Jerry Moran (Kan.) and Rob Portman (Ohio). Ayotte and Kirk are no longer serving in the Senate.

Five of the six female Republican senators made the list, which is consistent with what Michele Swers revealed in her research on Republican female senators: Female Republican senators are more likely than men to defect from their party on such “family” issues as education and health care (although not women’s health.)

Capito joined Collins and Murkowski in opposing all three amendments.

Senators from states with large groups of rural students tend to oppose vouchers

In Education Week, reporter Alyson Klein reports that senators from states with relatively high rural student populations tend to vote against vouchers — because there are few alternative schools for rural students to choose from. Therefore, allowing students to use federal funding to attend nearby public or private schools will not apply to or benefit rural communities.

According to the National Center for Education Statistics, Maine ranks fourth, Alaska ranks sixth, and West Virginia ranks 10th in the states with the highest percentage of K-12 rural schools in the United States. That means that these three senators represent states with especially high percentages of rural K-12 schools. Arguably, that accounts for Capito, Collins and Murkowski’s anti-voucher votes.

However, despite last-minute constituent protests, Capito voted for DeVos.

These three political factors may be behind Capito’s vote

Why the difference between Collins and Murkowski, on the one hand, and Capito on the other? Consider these three factors: which candidate each state voted for, the senator’s national teacher’s union approval rating and the strength (or lack thereof) of the state teacher’s union.

First, let’s look at how votes diverged among the three states. In Alaska and Maine, fewer voters pulled the lever for the GOP presidential candidate in 2016 than in 2012. The opposite happened in West Virginia: GOP presidential vote share increased from 62.3 percent in 2012, to 68.7 percent in 2016.

So Capito may be voting for Trump’s nominees because she believes her overwhelmingly pro-Trump voters want to give the president a free hand.

Second, Collins and Murkowski are the only Republican senators who received an “A” grade from the NEA in the 2013-14 congressional session. As a House member, Capito received a “C.” In the 2015-16 session, Collins and Murkowski are joined by Alexander as the only Republican senators with an “A” grade. Capito received a “B.”

Collins and Murkowski’s past grades signal their willingness to support the NEA’s strong position against vouchers and oppose a candidate like DeVos.

Third, Capito may feel less political pressure to vote in line with the teacher’s union because West Virginia adopted a right-to-work law in 2016. Alaska and Maine do not have right-to-work laws. According to the National Conference of State Legislatures, a right-to-work law prohibits labor unions from mandating union membership for workers, such as K-12 teachers. Once a state adopts a right-to-work law, that state’s teacher’s unions become less powerful, as they have fewer members, a smaller budget and can’t contribute as much to political campaigns.

Overall, the cross-pressures for Republican female senators and student demographics, such as the percentage of rural K-12 schools, may account for Republican senators’ opposition to vouchers. Among the anti-voucher GOP senators, Trump’s state vote share and teacher’s union support account for opposition to DeVos.

What do these numbers predict for the Trump’s legislation on student vouchers?

During the campaign, Trump proposed student vouchers in the education platform in his Contract with the American Voter. But passing any pro-voucher legislation in the Senate requires 60 votes — because that’s what it takes to prevent a filibuster and call for a floor vote on a bill.

Republicans have a 52-seat majority in the Senate. The roll call votes and the confirmation vote strongly indicate at least two Republican “nay” votes on any proposed pro-voucher legislation.

Simply put, Republicans may not have the numbers to pass voucher legislation in the next two years.

Mona Vakilifathi is a PhD candidate at the University of California at San Diego. Her interests are in state politics, lawmaking and charter schools.