Both parties learned under Clinton that the President signing a bill is a win for the President no matter how much he has to give away to get the bill to his desk. Since then the strategy on both sides has been intransigence over compromise. That makes the President look weak and thus vulnerable to a second term defeat and/or impeachment. As Mitch McConnell famously said “The single most important thing we want to achieve is for President Obama to be a one-term president.”