Don’t even think about it, Ben. That’s the message Capitol Hill is sending the Federal Reserve chairman regarding a possible third round of quantitative easing after Peter Diamond withdrew his nomination to join the Fed Board of Governors today.

The Nobel prize winner — Bernanke was once a student of his — certainly had the credentials. But the Senate had sat on his nomination for 14 months. Republicans objected to his support of the Wall Street bailouts and the Fed’s aggressive monetary policy, including its current “QE2” $600 billion Treasury buying program.

In the wake of Friday’s weak jobs report and a host of other disappointing economic data, concerns are growing that the U.S. recovery, long stuck in second gear, may be stalling out.

There’s some speculation that the Fed could adopt a new round of asset buys to replace QE2 when it ends on June 30.

But Diamond’s exit shows that any such QE3 would unleash a firestorm on Capitol Hill. Rep. Ron Paul, R-Texas, who is running for president once again, would gain even more allies for his anti-Fed crusade.

That’s just one reason why a new round of additional Treasury buys may be unlikely. Central banks in Europe, China, India and elsewhere are tightening, with many emerging markets grumble that the ultra-easy Fed has exacerbated their inflation concerns.

Within the Fed, several members have signaled they would oppose a QE3. Some fear the potential for higher inflation. Others wonder how much good yet another dose of monetary stimulus would do.

Indeed, as QE2 comes to a close, the program looks like less of a success than it did a few months ago. It did gaive at least a temporary boost to the prices of financial assets — stocks, bonds and commodities. That boosted consumer spending, especially on luxury goods as rising portfolios spurred the well-off to go shopping.

But that consumer boost peaked in October. Meanwhile stock and commodity prices have come under pressure lately. That could spur further weakness in consumers feeling the pinch of high food and gas prices. Home prices have continued to fall, hitting new post-bubble lows even as borrowing costs sank. And QE2 has failed to kick-start a sustained pickup in hiring.

Investors that cheered QE2 initially may see a third round of quantitative easing as a sign that the Fed has run out of ideas.

Republican (and some Democrat) lawmakers have expressed serious concerns with Fed efforts. QE3 would further politicize the central bank heading into the 2012 presidential race in which the economy will be the No. 1 issue.

More broadly, the Fed cannot remain independent if it maintains such a sweeping economic role. Pumping up asset prices, largely financing federal debt issuance (it’s been buying the bulk of new Treasuries), with no “civilian control” via elected officials is untenable long-term.

Many Fed-watchers expect policymakers to take only small action — continuing to roll over maturing assets into new Treasury purchases to prevent a de facto tightening.

Bernanke may offer some clues during a speech Tuesday. The next Fed meeting is June 21-22.