For more than 200 years, a safety barrier has protected our nation's courts and our democracy. No matter how controversial the case or unpopular the ruling, no state or federal judge has been impeached for an opinion issued from the bench.

In the next few months, that may change. The fight is being waged by political operatives in Iowa, but every state should be watching.

Last fall, Iowa voters ousted three high-court justices over a unanimous 2009 ruling permitting same-sex marriage. But the organizers behind that effort don't want to stop there - they've vowed to impeach and remove the court's four remaining justices, who weren't up for election in November.

The debate may have started over same-sex marriage, but the specter of impeachment has transformed it into an assault on constitutional government. Impeaching judges to redress political grievances would trigger a political circus that would paralyze government and undermine courts. Witch hunts against judges could also threaten state economies by driving out investments that create jobs, since businesses count on stable courts to settle disputes.

But there are deeper reasons why Iowans and Americans elsewhere need to catch their breath and avoid waging war on the courts.

Impeachments of judges were not designed as a tool for this kind of political disagreement, and the reason is essential to our democracy. If courts can't make tough calls, they won't be able to uphold the Constitution and protect our rights.

Impeachment is reserved for serious misconduct. In Iowa, the standards for impeaching judges are "misdemeanor" and "malfeasance" - in other words, committing a crime or violating one's oath of office. Other states, and the federal Constitution, have similarly demanding standards.

Keeping courts off-limits to political impeachment has benefited everyone. Take last year's Citizens United decision, in which the U.S. Supreme Court ruled 5 to 4 that corporations and unions could spend unlimited money in elections.

Most Americans disagreed. But imagine for a minute that congressional Democrats, with majorities in both the House and Senate, had impeached the five justices behind the majority opinion and subjected them to Senate show trials.

The trials would have shut down the government and spread the word that judges shouldn't follow the law but rather opinion polls and party bosses. And politically driven impeachments would cause generations of acrimony, leading to endless payback trials against judges appointed by both parties.

There's a reason this all sounds so radical. It's been seriously tried only once in our nation's history - in 1805, when Thomas Jefferson tried to oust Justice Samuel Chase, whose crime was that he belonged to the opposition Federalist Party. Senators across the political spectrum rejected the idea. Congress hasn't tried it since, even though courts have made unpopular decisions on just about every imaginable controversial issue, including slavery, segregation, abortion, gun rights and presidential elections.

Iowa citizens, no matter what they think of same-sex marriage, want their legislators to work on policy issues through proper channels, not by settling political scores. Americans everywhere should hope that the impeachment bogeyman gets put to bed.

Bert Brandenburg is executive director of Justice at Stake, a nonpartisan organization that defends courts from political attacks.