Welfare reform proved conservatives right in a very public way, notice no one is campaigning on restoring it to its former form. This is a source of frustration for the Left.
"Tax cuts will harm the economy" was for years a very powerful anvil with which to club conservatives, and recent elections prove that the mantra has lost its potency, no doubt due to the very public repudiation of such nonsense in the recent Bush cuts and subsequent uptick in the economy.
More important perhaps is the exposure through events of the Democrats "kinder gentler", appease and apologize foreign policy not only as impractical, BUT DOWNRIGHT DANGEROUS. These are results for all to see, and no amount of pretzel logic and media spin can change what the people see and feel.
The media has indeed enabled the Left to live these lies for some time, but the results of their policies have come home to roost in recent years in very public, emotional, and therefore opinion changing ways, and it's my opinion that these public exposures are the cause of all the anger and hate we see from the Left these days.