It's been a big week for Wisconsin Gov. Scott Walker. On Monday, he announced his candidacy for the Republican nomination for president. On Thursday, he was able to watch as a dark chapter of his state's history finally came to an end.

That chapter had begun after Wisconsin's political Left lost its power at the ballot box, then seethed as its special privilege of living at the state's expense was taken away by Walker's reforms of the collective bargaining process.

The media gave ample coverage to the street protests that occurred at that time in 2011, but the more important reaction was going on behind closed doors. Local Democratic prosecutors chose at that point to abuse their public offices and initiate a campaign of harassment and suppression against their political opponents. They did so on the thin pretext that a campaign finance law had been broken.

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In the course of their secretive investigation, these prosecutors deliberately employed Gestapo-like tactics in order to make a point. Pre-daylight raids were conducted on private citizens' homes as if they were violent fugitives. All manner of documents completely irrelevant to their investigation were taken — even family photographs were seized — for the sole purpose of intimidation.

Those subjected to this special treatment were forbidden from speaking publicly — something allowed under Wisconsin's unusual "John Doe" statute, which the state legislature should probably revisit at the earliest opportunity.

Fortunately, the victims of this witch hunt did not remain silent, instead coming forward and suing to end their persecution. They finally prevailed Thursday as Wisconsin's Supreme Court handed down an unusually emphatic decision. "To be clear," the majority wrote, "this conclusion ends the John Doe investigation because the special prosecutor's legal theory is unsupported in either reason or law."

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In short, the court concluded that prosecutors could not even show they had an actual crime to investigate in the first place. Their allegations of political coordination, even if true, would constitute activity that is protected in this country by the First Amendment.

But of course, preventing or fighting crime was never the point of their investigation. Its real purpose was two-fold:

First, it was about revenge — that is, getting back at Walker for weakening their power base, the state's public sector labor unions. Second, it was about creating a short-term political advantage for themselves. The investigation helped suppress the political activity of the opposition during the 2014 election cycle, during which time they hoped to oust Walker from office despite nominating a relatively unknown candidate. They only narrowly failed.

There is one very good reason Wisconsin Democrats had to sink so low, and it is the very same reason Walker is now a serious contender for higher office. His public-sector union reforms worked, saving taxpayers $2 billion in their first year alone. They helped Wisconsin school districts, counties and municipalities maintain full public services without layoffs or austerity.

No serious person who understands the situation in Wisconsin disputes this. That's why the reforms are now so popular in the state — and it's also why no Democratic politician, including Walker's 2014 opponent, would dare campaign on a platform of trying to undo them.

Walker has a much bigger and broader case he will have to make to Americans if he wants to be their president. But for now at least, it's a new day in Wisconsin, and that's something everyone can be happy about.