Editor's note: The following column first appeared in The Hill newspaper and on TheHill.com.

What will it take for Hillary Clinton to lock down union endorsements?

At this week’s Democratic debate in Las Vegas, there will be competition for one whale of an endorsement – that of the AFL-CIO. 

The backing of two other big unions, the Service Employees International Union (SEIU) and the American Federation of State, County and Municipal Employees (AFSCME), is also up for grabs.

In cases where Hillary Clinton has made progress in winning union endorsements, her success has had little to do with economics. But the price of the teachers’ unions endorsements could be much more costly to the nation than any trade deals.

This comes as the International Association of Fire Fighters (IAFF) recently pulled back plans for an early endorsement of Clinton, hoping to gain added leverage on her economic agenda. The IAFF is especially eager to counter the enthusiasm for trade deals exhibited by the two most recent Democratic occupants of the White House, President Bill Clinton and President Obama.

Union membership rates have been diving in the private sector for years. Nationwide, across the public and private sectors combined, only 11 percent of employees are members of a union. The conservative majority on the Supreme Court could end mandatory union dues – the foundation stone for powerful union contributions to Democrats – as early as next year.

But, right now, American unions, with their money and on-the-ground organizing ability, remain a critical constituency for Democrats in general, and candidates for the party’s presidential nomination in particular. 

In 2008, Clinton’s loss of several union endorsements to Obama, then a first-term senator representing Illinois, proved damaging to her campaign. Now her camp has a similar fear of losing union backing to Sen. Bernie Sanders (I-Vt.), in part because of his relentless focus on stagnant wages and income inequality.

That’s why the political marketplace is wide open for candidates willing to make deals to win union endorsements.

Last week, Clinton made a major move to get in line with the AFL-CIO’s agenda. She announced her opposition to a key Obama administration free-trade deal – the Trans-Pacific Partnership Agreement, or TPP —  agreed between the U.S. and 11 key trading partners. Clinton had previously heralded that accord, both as secretary of State and in her recent memoir.

Sanders long opposed the trade deal. “All I can tell you, whether it is the Keystone pipeline, whether it is TPP, these are issues that I have had a very strong opinion on from day one," Sanders told reporters last week. "And I can simply say I am delighted that Secretary Clinton is on board ... To be very frank with you, it would have been more helpful to have her on board a few months ago."

Clinton has also been slow to warm to a big hike in the minimum wage. Both Sanders and former Maryland Gov. Martin O’Malley back a $15 minimum wage. So far, Clinton is only willing to go to $12.

Sanders and O’Malley have called for tighter federal control of big banks, specifically pulling them out of the investment business. Clinton has resisted such steps.

“In terms of Wall Street,” Sanders said last week, “three out of the four largest banks today are bigger than they were when we bailed them out because they were too big to fail... I think we should eventually break up these large financial institutions, which today have too much economic power.”

When Clinton recently announced her opposition to building the Keystone XL pipeline, it was a big win for environmentalists in the Democratic coalition. But some unions had backed the pipeline as a potential source of jobs. Now the unions want to see attention paid to their agenda.

Richard Trumka, the president of the AFL-CIO, said in August that he wants to see who will be advising Hillary Clinton on economic issues.

He explained that if Wall Street advisers of a similar ilk to those featured in the Bill Clinton and Obama White Houses populated a Hillary Clinton administration, “you are going to get the same results and the same results are not good enough for working people.” 

In cases where Hillary Clinton has made progress in winning union endorsements, her success has had little to do with economics. But the price of the teachers’ unions endorsements could be much more costly to the nation than any trade deals.

Last week, Clinton netted the endorsement of the National Education Association, the NEA. It is the biggest union in the country with three million members. She can now call upon the support and money of the nation’s two largest teachers’ unions. The American Federation of Teachers (AFT) endorsed her earlier this year.

School children and parents don’t have a union. But if they did, their union would be screaming that U.S. public schools lag behind student achievement in most other developed nations. The black and Hispanic student experience in America’s big city schools is still a public scandal, troubled by high dropout rates and low academic achievement.

The NEA that endorsed Clinton remains opposed to major school reform efforts, including the expansion of charter schools.

Clinton is now aligned with a union that fought against the Obama administration’s effort to reward school districts for measuring academic outcomes, including standardized tests, and opposes most teachers’ evaluation on the basis of student testing.

The unions have engaged in bitter battles with outgoing Education Secretary Arne Duncan over his support for charter schools.

Clinton personally traveled to NEA headquarters in Washington and did a 90-minute question-and-answer event with the NEA board. Clinton and her Democratic rivals have shunned an invitation to an education reform forum because it was sponsored by former CNN anchor Campbell Brown. Brown is a supporter of charter schools, and an activist on the issue. She has also questioned why public school teachers have tenure protection even if their students fail to learn. 

Randi Weingarten, the president of the AFT, has dismissed Brown as pushing a “test, punish and privatize” agenda for public schools. 

Out of apparent fear of antagonizing the unions, Clinton, Sanders, O’Malley, former Virginia Sen. Jim Webb and former Rhode Island Gov. Lincoln Chafee have all turned their back on Brown’s invitation to discuss their ideas for improving schools.

The price of a union endorsement is too high for school children.

Juan Williams is a co-host of FNC's "The Five," where he is one of seven rotating Fox personalities.