<font color="blue"> "Since all but a few states already collect a sales tax, increasing it slightly would be very easy." </font>
Ah, if it were but a slight increase, it might be palatable. I did a Google search on "national sales tax" and came up with a few well-documented studies on how it would work. There were written by proponents of such a system, so if there was any bias, it would be in favor of the sales tax.
Essentially, what they are talking about is a 15% (some are higher) national sales tax collected by the states as you suggest, with rebates or credits for purchases up to the poverty level - the first $18K plus of purchases would be tax free.
Sounds pretty good, until you remember that the states will still be collecting their sales tax, as well -- averaging somewhere around 6 - 7% or more, with the result that in some cases, the tax on a purchase might approach 25%! Then, they sneak in the idea that while there would be no income tax, there would still have to be a payroll tax, administered by the Social Security department, to cover Social Security and Medicare. This is in addition to the 15% national tax. Since many people, including my wife and I, actually pay more in FICA and Medicare taxes than we do in income taxes, this would result in a HUGE tax increase.
The simple fact is that you can tax and spend, as is often pinned on one party, or you can borrow and spend, as is the case with the current majority party, or you can cut spending, which neither party shows any propensity to do. There are no magic bullets -- if you're going to spend, you have to raise the money somewhere to do it. You may shift the burden around with different tax schemes, but in the end, everyone will pay more if there is no cut in spending.
Of course, the problem is that with the exception of waste and fraud, there really is no easy way to cut spending. That's why even the conservative party is still spending it. As one example, think about the party that was going to abolish the department of education a few years ago, and now brags about "No Child Left Behind" as one of it's maor accomplishments. By the way, before anyone punches the "notify moderator" button, this is not a bash on either party, just a statement of fact.
I think one of the primary reasons these schemes are floated by politicians is because most of them are sneaky ways to raise taxes without seeming to do so.
Frankly, the present tax system is the one in which I pay the lowest taxes. Most of our investments have been in various forms of real estate, and rental real estate just happens to be one of the neatest loophole providers ever invented. We're self-employed so we pay the max on SS and Medicare, the full boat employer's and employee's shares, on all the dollars we earn after expenses. However, once our income gets past that and into real estate stuff, the loopholes knock such a hole in the dollars that are left that we pay barely a pittance in comparison to the FICA. There's no way on earth that I'd favor a national sales tax or a flat tax.
Not fair, you say? You don't have access to those breaks? Pshaw. I'm far from a wealthy man, but we chose to structure it that way, and the same choices are available to everyone.