So let's grab a Bill of Rights and try to understand why this amendment has become a favorite of the tea party and other small-government conservatives, and why some candidates laud its virtues.
The amendment says any powers not delegated to the federal government "are reserved to the states . . . or to the people."
The words reflect Founding Fathers' concerns that the Constitution might hand too much power to a central government. But it's little wonder people still debate the meaning of the words. Even the Supreme Court said in 1931 that the amendment "added nothing" to the Constitution.
"There's no help at all in telling what is, in fact, given to the national government and therefore what is reserved to the states," said Sanford Levinson, a constitutional-law professor at the University of Texas who is now a visiting professor at Harvard.
Even so, the amendment has a following. There's a Tenth Amendment Center, a California-based group that advocates strictly limited government. Supporters call themselves Tenthers.
They "like the idea that states should be able to make their own choices," said Michael Boldin, the group's founder. "It doesn't matter what side of the political spectrum you're on."
In the Iowa debate, former Massachusetts Gov. Mitt Romney cited the 10th in contrasting his state's health-care law to President Obama's. Texas Gov. Rick Perry wrote in his 2010 book, Fed Up! Our Fight to Save America From Washington, that state and local governments should play a greater role than federal authorities.
"From marriage to prayer, from zoning laws to tax policy, from our school systems to health care, and everything in between," Perry wrote, "it is essential to our liberty that we be allowed to live as we see fit through the democratic process at the local and state level."
But former Sen. Rick Santorum (R., Pa.) warned against letting the 10th Amendment "run amok." He said issues such as abortion and same-sex marriage are better handled federally.
Boldin said he takes politicians' comments in stride. "Most politicians who talk about it, I believe, are pandering," he said Wednesday.
Steven Schwinn, a constitutional-law professor at the John Marshall Law School in Chicago, finds it interesting that some candidates voiced support for states' rights - yet want the federal government to intrude into a private area: marriage.
In pre-Constitution days, Schwinn said, the Articles of Confederation gave more explicit powers to states and "really tied the federal government's hands." He said the Constitution's authors didn't opt for such strong words in the 10th Amendment, adopted in 1791 as part of the Bill of Rights.
Today's Republicans, Schwinn said, seem to want to revisit a states-vs.-federal battle that was "lost back in the late 18th century."
What's new this time around, Levinson said, is a conservative view of Washington that has not been put forward since the New Deal's expansion of the federal government. In the years since then, he said, most Republican presidents and candidates have largely accepted the New Deal.
"Even though Reagan rhetorically attacked big government, he didn't do much about it," said Levinson. "Now you have people like Perry and [Rep. Michele] Bachmann who really hate the national government."
Levinson said the 10th Amendment had become more like a "mantra" in today's version of the late-18th-century debate. "It's a reminder that the national government shouldn't and can't do everything," the law professor said, "and there has to be something reserved for the states."
Need a down-to-earth example of all this lofty talk of state vs. federal powers? Here's one: The 10th Amendment is the focus of an appeal by a Montgomery County woman, convicted of trying to poison her husband's pregnant girlfriend.
Carol A. Bond, charged under a federal chemical-weapons law, is serving a six-year prison term. Her lawyers argue that her actions amounted to a crime of passion, better suited for state charges than a federal law aimed at terrorists. The Supreme Court ruled in June that Bond can challenge her conviction on that ground.
If convicted in state court, her lawyers contend, the Lansdale woman would likely have faced just three to 25 months in jail. They say, in essence, that Uncle Sam should stay out of this one.
They just don't call themselves Tenthers.
The 10th Amendment
"The powers not delegated to the United States by the Constitution,
nor prohibited by it to the states,
to the states respectively, or
to the people."
Contact staff writer Emilie Lounsberry at firstname.lastname@example.org.