It's the general principle of "compromise", most notable in the (IIRC) 1999 "response" to Clinton's SOTU speech; for each new program Clinton suggested, the Republican spokes-critter offered a "Democrat lite" version, rather than simply stating that any of the proposed programs were simply Bad Ideas. Democrat lite is an absolutely unsupportable position, but it's what Republicans usually seem to take.
You're talking about "pork". Both sides do it, and they will continue until voters stop rewarding them for it. That has nothing to do with ideology - it's only got to do with greed. And too many of us have that.
The current SS debate is a good example - the issue is over who thinks they can get the most money from other people. Bush is losing because many people think they won't get others to pay for their retirement.
If people thought about what made sense more than what they could get from others, it wouldn't be an issue. But this is what happens when people think they won't get as much money from the public dole as they could.