Republican candidates are encouraged (in a if-you-know-what's-good-for-you vein) to sign the tax pledge dreamed up by Grover Norquist and his Americans for Tax Reform. Some wiggle room is allowed to increase one tax while decreasing another. Of course. This is the only way Republicans can achieve their Powerball Jackpot for the Wealthy — a platform plank that calls for elimination of the income tax, which would be offset by something "equitable" (in the original draft version by an increase in the sales tax, a mathematical impossibility that cooler heads ultimately edited out). The likely alternatives would be a punishing burden on working people and likely combined with drastic cuts in government services on which working people depend, like medical care for pregnant women and their children.
A letter from from Rep. John Burris also outlines the quid pro quo on the no-tax pledge:
Finally, based on the 2010 general election cycle and the 2012 primary election cycle, it is safe to assume that outside groups will in large part support only candidates who sign the pledge. It can make a difference in their race.
Reports have circulated for days of specific independent campaign finance offers from outside groups to candidates who sign the no-tax pledge. Of course. If, say, the Kochs were to spend $250,000 or so to buy sufficient legislative seats to control the Arkansas legislature, they'll make it back many times over in income tax cuts before another year is gone. This is tax fairness in Burris World.
Is it legal to promise a campaign contribution in return for a vote? Not that anybody has done that here. Except in a manner of speaking.