In its coverage of the U.S. Senate confirmation hearing on President-elect Donald Trump's pick for education secretary, The New York Times’ headline read: “Betsy DeVos’s Education Hearing Erupts Into Partisan Debate.”

To understand how politics took center stage in a hearing about education requires understanding the influence unions have on elections and the interests that Democratic politicians support.

State and national public school employee unions have been among the most vocal critics of DeVos’s nomination because of her long history of supporting school choice.

In addition to enabling parents to choose their own children’s educational path, choice undercuts the financial strength of the public school employee unions that feed the Democratic Party political machine.

In most states, the growth of charter schools also means the growth of a non-unionized workforce in public education. Under current Michigan law, conventional public schools are required to engage in collective bargaining with teachers unions. This law does not apply to the nonprofit or for-profit management companies that most charter school boards hire to operate their school, however.

So just six of the nearly 300 charter schools in the state have a unionized workplace, according to the Michigan Association of Public School Academies.

In 2015, there were about 10,200 charter school teachers in Michigan. The vast majority of these positions are non-unionized. Some of those charter school teachers would surely be dues-paying union members if they worked in conventional public schools instead.

And public school employee unions overwhelmingly support Democratic political candidates and allies. When those candidates become elected officials, the vast majority return the favor by opposing laws that help or expand charter schools, and supporting laws that restrict them.

The American Federation of Teachers made $9.7 million in campaign contributions in the 2016 election cycle and 100 percent of that went to Democratic candidates or progressive political groups, according to OpenSecrets.org. Most of those groups also oppose school choice, but some promote progressive causes unrelated to public education.

The National Education Association gave $27.8 million in campaign contributions in 2016, 99 percent of which went to Democrats or to groups aligned with the union’s positions.

The Michigan Education Association endorsed 75 candidates for House seats this November and all but three of them were Democrats.

The Michigan chapter of the American Federation of Teacher made a $7,500 campaign contribution to the Michigan Democratic Party in 2016.

But supporting political candidates is only one way the teachers unions give to progressive organizations that also oppose school choice.

The MEA funded a broad network of such organizations in 2016, according to a report it filed with the U.S. Department of Labor.

Both the AFT-Michigan and MEA gave to a national progressive nonprofit called America Votes. The MEA gave $50,000 while AFT-Michigan gave $15,000.

America Votes coordinates progressive political campaigns across the country, including in Michigan. It advertises itself with this slogan: “The coordination hub of the progressive community.”

American Votes President Greg Speed is the former communications director for the Democratic Congressional Campaign Committee.

The MEA also gave $20,000 to the Michigan League for Public Policy and $10,000 to the Great Lakes Center for Education Research and Practices. Both organizations produce studies and comment on issues in ways that align with the MEA’s political agenda.

The MEA also gave $91,500 to Progress Michigan, a political activism group that opposes school choice and advertises itself as “Uncompromised progressive politics for Michigan.”

And the MEA gave $5,000 to Chris Savage, the president of the Washtenaw County Democratic Party who also runs the far-left blog Eclectablog, which also opposes public school choice.

Lonnie Scott, executive director of Progress Michigan, and Savage both said in emails that the contributions didn’t impact how they reported on charter schools on their websites.