XVII is pretty simple -
No law, varying the compensation for the services of the Senators and Representatives, shall take effect, until an election of representatives shall have intervened.
While the most recent amendment (as of this writing), its origins lie with the Founder of Founders- credit James Madison. And it was so important to him, he had it as one of the originally proposed 12 amendments we know as the Bill of Rights. Let's let James remind of us its importance-
"There are several lesser cases enumerated in my proposition, in which I wish also to see some alteration take place. That article which leaves it in the power of the legislature to ascertain its own emolument is one to which I allude... There is a seeming impropriety in leaving any set of men without control to put their hand into the public coffers, to take out money to put in their pockets; there is a seeming indecorum in such power, which leads me to propose a change... I have gone therefore so far as to fix it, that no law, varying the compensation, shall operate until there is a change in the legislature; in which case it cannot be for the particular benefit of those who are concerned in determining the value of the service."
That makes sense, you give someone the power to enrich themselves, and they will. This power must be checked, and it cannot be balanced by the other branches, lest they then sit subservient to one another. No, the final arbiter must the voters. It took over 200 years, and an incredibly unpopular congress (ha!), for the states to get their acts together to ratify, but it's the law of the land now. NY, Mass, Penn and Mississippi are sitting this one out- hard to think of anything else those four states might possibly agree on...
So why does XVII matter? Congress can pass COLAs (those smallish cost of living adjustments)- probably- the Supreme Court hasn't weighed in, declining to take up John Boehner's (yes, that John Boehner) appeal that COLAs violated XVII. Putting that matter aside, the real meat is the power of self-emolument. Congress should act in the interests of those it governs, and if it chooses to wield that power to attain self-enrichment, by all means- but those gains must wait until the voters decide to keep them in power.
Which brings us to the tax plan the House and Senate are in the midst of debating/hiding/passing. The exact language is a mystery, because it is abomination. What we do know is that it will most assuredly enrich the rich- who, lo and behold, are vastly over-represented in Congress. One example of the height of brazenness, Bob Corker, who's life mission was decreasing the deficit, was bought off with an update to this bill that directly enriches him. He is not running for election, which is fine, there is an abundance of hypocritical hacks stalking the hallways already, this fish couldn't rot anymore from the head down. But the 27th amendment demands that this enrichment does not take place until the next election. Which means whatever middle and lower class murder spree the GOP is about to pass cannot take effect until an election has intervened.
Unless, of course, the President and every member of Congress chooses to lay open their finances and definitively show that this law will not substantially vary the compensation of our elected officials. Which will never happen because the Republican Party has taken us all for fools, and is sending us the bill.
The least we all can do now is vote.