Let me make myself clear if you're not up on all the buzzwords.

There are two types of stimulus that can be foisted upon the American economy:

"Monetary" stimulus is what the actions of the Federal Reserve are. Lowering short-term rates to induce bankers to lend, the "QE" programs which buy up various types of debt to force rates lower and liquidity higher... those are monetary policy. The Fed can make those moves unilaterally, and they have. QE3 would be monetary stimulus. The problem of the liquidity trap directly goes to the heart of how effective a QE3 could be... which is, any QE3 by the Fed would be hugely expensive to achieve any results.

The more common stimulus is "Fiscal," which means the government creates (via legislation or regulation) policy which spends tax monies on ... whatever. These take either a vote of Congress on legislation, or the Office of the POTUS needs to make a regulatory change on money that is already allocated to an executive agency. For example, the POTUS could re-direct monies already in the USDA budget from research to hiring people to do weed control, or something similar.

A fiscal stimulus could counter-effect a liquidity trap, because Congress could say "We direct you to spend this money, make this investment, hire these people. Period. Do it, and do it by this date!" This would effectively remove the private sector from the loop on initiating private sector investment.

Why is fiscal stimulus "off the table?"

The fiscal stimulus in this recession has been more of the "Chicago style" of stimulus - paying off public sector employees by way to funneling money into the state coffers to prop up the salaries, bennies and pensions of state and local government employees. A mere pittance of the nearly $900 billion allocated for the ARRA actually made it into the private sector. Recently, Mr. Obama said, "those shovel-ready jobs weren't as shovel-ready as we thought," proving that Harvard graduates really are smart enough to see the truth... they just take a few years longer than everyone else to have said truth penetrate their skulls.

The current  reckoning is the jobs "created" by the ARRA cost the taxpayers about $278K per job, and many of these jobs have turned out to not have much economic multiplier. Some economists now argue that the ARRA made the recovery worse, not better, and Congress would be well advised to not repeat this shameful performance. We had a chance for effective stimulus, and the welfare state mentality embraced by the Democrats caused them to use money for transfer payments (ie welfare) and political grease, rather than on jobs with effective economic multipliers.

At any rate, the two parties are now engaged in a deathmatch struggle over cutting spending. Chances of increased spending are simply out the window now. There is only talk of either raising taxes to support the current level of ineffective spending or cutting spending. There's no talk of  a new round of fiscal stimulus.