Part of the Washington Examiner's weeklong commentary series on labor unions. To see the entire series, click here.

In his 2014 State of the Union address, President Obama urged Congressional support for major trade deals with the European Union and Pacific Rim countries.

The very next day, Senate Majority Leader Harry Reid, D-Nev., rebuked the president, saying he would not allow votes on the deals. “Everyone would be well-advised to not push this right now,” he said.

Celeste Drake, a trade policy specialist with the AFL-CIO, was delighted. This was “a great opportunity to get off the fast track to bad trade deals and open the policy window to a better deal for workers,” she told the Wall Street Journal.

Drake's comments illustrate why Reid had little choice but to humiliate a president of his own party. To keep control of the Senate, he had to keep the Big Labor money spigot open. And that meant not crossing the unions.

Big Labor has donated $934 million to candidates for political office and parties in the last decade and a half, $755 million of which went to Democrats and liberal groups, according to the Center for Responsive Politics. That's just the spending reported to the Federal Election Commission. A 2012 study of Labor Department filings by the Wall Street Journal found “an additional $3.3 billion that unions spent ... on political activity,” such as polling fees and get-out-the-vote expenses, which aren't required to be reported, between 2005 and 2011.

The day after the 2012 election, Big Labor boasted that it won the election for Obama by driving up Democratic turnout in key swing states like Pennsylvania and Ohio. “You take the unions out of Democratic politics and you will see a lot less Democrats elected, because they supply the money and the manpower,” said Mallory Factor, author of Shadowbosses, a study on union political spending.

Big Labor's spending has grown even higher after the Supreme Court's Citizens United v. FEC decision in 2010, which lifted restrictions on political spending. Though most liberal groups slammed the ruling because it allowed corporations to spend more, the AFL-CIO benefited from it.

Unions are also big spenders on lobbying Congress: The Center for Responsive Politics puts the total at $584 million since 1998. The average annual amount is $37 million and rising. It topped $50 million in 2011. In 2013, labor had 450 registered lobbyists.

Bear in mind that union dues are primarily supposed to offset the costs of collective bargaining. But unions often ignore that. In the 1988 Supreme Court case Communications Workers of America v. Beck, CWA was found to have been spending only 21 percent of its dues on collective bargaining.

Beck established that unions could only demand workers covered by its contract pay for collective bargaining expenses. What it didn’t do was create a system for monitoring this. Workers typically must sue the union to force disclosure, and the Obama administration has rolled back federal disclosure requirements.

What does Big Labor get in return for this spending? It is not a coincidence that much of the domestic policy Congress has considered over the past decade has been labor-related. Union pressure was instrumental in getting the federal government to bail out GM and Chrysler in 2009, an effort that cost taxpayers an estimated $10 billion but saved the United Auto Workers.

Big Labor was a major supporter of President Obama's $831 billion economic stimulus bill, which it thought would provide billions to unions through “shovel-ready” infrastructure projects and loans to green-energy companies.

Obama's Affordable Care Act was another bill that received heavy union backing. In deference to Big Labor's wishes, Obama delayed a tax on high-end insurance plans -- intended to get the rich to finance the law -- until 2018 because many unions provided them to members. Last year, Obama helped them again when he excluded union insurance plans from the law's reinsurance fee. He did this by raising the fees on everyone else.

The recent congressional push for a comprehensive immigration bill was put on hold until the AFL-CIO and the Chamber of Commerce could strike a deal on a set of common principles. The AFL-CIO insisted on limits on any temporary guest-worker program as well as visas for high-tech workers, provisions which became part of the Senate-passed version.

Senate Majority Leader Harry Reid's push to end the Senate filibuster for most nominees came largely due to labor pressure. The White House consulted with the AFL-CIO in choosing nominees to the Labor Department, National Labor Relations Board and Consumer Financial Protection Bureau, and the organization was eager to see them confirmed. One, NLRB member Nancy Schiffer, was a top lawyer at the AFL-CIO when she was nominated.

And that effort has paid off. Since being confirmed, the labor-backed officials have charged Walmart with illegal firings, dismissed fraud charges against the United Auto Workers (despite finding some evidence of fraud) and resurrected a speedy workplace organizing rule business groups call the “ambush election” rule.

“There is no question they are in labor’s pocket,” said Peter Morici, professor of economics at the University of Maryland.

The current congressional push to raise the minimum wage to $10.10 is largely Big Labor's doing as well. Higher minimums make low-wage, non-union labor less affordable for businesses. Some service industry unions negotiate contracts that tie their members' wages to the minimum, meaning an increase also raises their members' wages.

The Democrats' unwillingness to consider entitlement reform is also partly due to fear of Big Labor. “Let me just say this one for the record. No politician -- I don't care the political party -- will get away with cutting Social Security, Medicare or Medicaid benefits. Don't try it. And this warning goes double for Democrats. We will never forget. We will never forgive. And we will never stop working to end your career,” AFL-CIO President Richard Trumka said in October.

Big Labor doesn't get everything it wants. Card Check legislation, the main item on its wish list, was proposed in 2009 but went nowhere. An effort to bail out union pension plans in 2010 also quickly died, as did talk to bail out bankrupt Detroit last year.

In these cases, labor’s requests go too far even for many Democrats. But these things died quietly for a reason. Democrats know better than to bite the hand that feeds them.