Republicans support tax cuts that affect very high incomes. Democrats don't. They support tax cuts only up to income levels that include the middle class and the poor.*

Ah, but how do you define "middle class"? For a while now, Obama and the Democrats have drawn the line at household incomes of $250,000 a year. That's a rather high definition, since median household income is around $50,000 a year. But now some Democrats aren't even comfortable with that threshold. According to Mike Allen at Politico, they say they want to draw the line at $500,000, or maybe even a million.

The American Prospect's Jamelle Bouie objects:

Regardless of where or how you choose to spend your money, a six-figure income of $500,000 means that you are rich, period. You make more than ten times the median household income, and given your most likely occupation--financial services--you have been the chief beneficiary of economic growth for at least the last decade. If this were a sane country, we wouldn't even consider giving you a tax cut, because you don't need it.
Of course, given the choice between tax cuts for some of the nation's rich people and tax cuts for all of them, I'll take the former without question. Still, let's not delude ourselves into thinking a half-million dollar income isn't rich. Without question, it is.

Yes it is. And, remember, cutting taxes for the very wealthy is one of the least efficient ways to improve the economy. These are precisely the people most likely to save money, rather than spend it. 

Meanwhile, raising the income threshold for tax cuts has an impact on the budget. I don't know exactly how much it costs to reduce taxes on incomes less than $500,000 or $1 million, as opposed to incomes less than $250,000. But I know what will happen, broadly speaking.  The more we cut taxes in order provide extra help to the McMansion Middle Class, the more we deprive the government of revenue. That means some combination of cuts to popular programs and, more likely, higher deficits.

Gee, do you think some of Democrats telling Allen they want the higher threshold also describe themselves as fiscal conservatives furious over rising deficits?

*Reworded to point out that rich people still get big tax cuts when the cuts stop at higher incomes. When you cut taxes for incomes under $250,000, for example, somebody making a million dollars a year gets a tax break on the first $250,000 of taxable income. That person just wouldn't get a tax break on the rest of his income. Thanks to reader "stanalama" for reminding me to make that distinction clear.