The Supreme Court may have just signaled the end of the union era in politics

The ruling said, simply, that public-sector unions can no longer require non-union workers to pay fees that allow unions to collectively bargain. The practical effects of that decision are that unions will lose considerable bargaining power and that union membership could well sink.

That's a vicious cycle that union allies insisted was aimed at reducing the political power of unions, which for decades were one of the pillars of the Democratic Party's success -- particularly when it came to organizing efforts.

This court decision comes almost a decade after Wisconsin Gov. Scott Walker won a years-long battle to drastically reduce collective bargaining rights for public employees in the Badger State. Walker beat back a recall effort driven by distaste with collective bargaining move -- and is running for a third term in 2018.

What Walker's gambit on public employees has wrought in Wisconsin should serve as a warning to union supporters nationwide. According to the Milwaukee Journal Sentinel, membership in the Milwaukee Teachers Education Association has dropped 30% since Act 10 -- the collective bargaining law -- went into effect.

And it's not just Milwaukee -- as this terrific Journal Sentinel piece notes:

"Nationally, no state has lost more of its labor union identity than Wisconsin since 2011, a Milwaukee Journal Sentinel analysis found. Union members made up 14.2% of workers before Act 10, but just 8.3% in 2015. That was nearly double the drop of Alaska, the runner up."

Those numbers are striking. And it's not as though organized labor had been prospering as a political force in recent years.

In 1976, 29% of the electorate said they or someone in their household was a member of a union. In 2016, that number was just 18% -- matching its low ebb. (Just 18% of the electorate was made up of union members in 2012 as well.)

The decline in unionized voters is an acute problem for Democrats -- given that organized labor has been a reliable bloc of the party's base for decades. With the exception of Ronald Reagan's 1980 and 1984 victories, the Democratic presidential candidate has won the union vote by double digits in every election since 1976. Until 2016, that is, when Hillary Clinton only beat Donald Trump by 8 points.

Speaking of Trump, he celebrated the court decision via Twitter on Wednesday morning.

Tweeted Trump: "Supreme Court rules in favor of non-union workers who are now, as an example, able to support a candidate of his or her choice without having those who control the Union deciding for them. Big loss for the coffers of the Democrats!" Court precedent, however, long held that you couldn't force non-members to pay fees for political activity -- Wednesday's ruling was about fees charged for issues related to collective bargaining.

Trump's tweet gets at the long-held belief among conservatives that organized labor is functionally an arm -- or, maybe better put, an ATM card -- of the Democratic Party. Conservatives have long maligned union spending on Democrats in elections.

In the 2016 election, labor unions spent more than $217 million on political activities, with that money overwhelmingly going to Democratic candidates, according to the Center for Responsive Politics. The American Federation of State, County and Municipal Employees (AFSCME), for example, donated 99.4% of its contributions to Democrats.

Liberals push back by saying the likes of Sheldon Adelson and Robert Mercer -- among others -- poured tens of millions of dollars into the 2016 campaign, entirely on the Republican side.

The court decision Wednesday is likely to accelerate union struggles -- both in terms of labor's organizing ability, bargaining power and political might. Whatever the motivations of the case -- and liberals and conservatives vehemently disagree about them -- the result is hard to dispute: A further diminution of organized labor in American life and its politics.