THE Bush administration might these days recollect that old saying: Be careful what you wish for, you might get it.President Bush and his predecessor wanted conservative policymakers at the Federal Reserve. They appointed them. Now Mr. Bush is reaping the consequence - a firm monetary policy that has resulted in an unusually modest economic recovery. On the good side, that policy means a low inflation rate. But the economy may well not feel prosperous at election time next fall, damaging the president's election prospects. (Something similar could be said for the Supreme Court: If votes by conservative Reagan-Bush appointees add impetus to the abortion issue, it could cost Bush many women voters.) A nervous White House has been periodically calling for lower interest rates and faster growth in money, regarded as a lubricant for the economy. Presuming there is a credit crunch, Bush last week approved a series of regulatory measures aimed at encouraging banks to make more new loans. The news won't improve the forecast of most economists. Those at the Organization for Economic Cooperation and Development are about to issue a report on the United States economy predicting real growth next year of only 2.5 percent. The average 1992 forecast for the US of 48 economists from several nations compiled by the newsletter Globescope (Glen Carbon, Ill.) is similar - 2.4 percent. Sam Nakagama, a Wall Street economist, is troubled by the slow growth in a broad measure of the nation's money supply known as M2. Over the past three months, M2 has declined at a 0.3 percent annual rate; over six months it has grown at a 2.2 percent rate, below the Fed's target range for that measure of 2.5 to 6.5 percent. "It is obvious that the Fed board has been inexcusably complacent in its policymaking," Mr. Nakagama states. As a result, he forecasts slow growth in national output over the next year. However, some other economists look to a narrower definition of money, M1, and are less worried. M1, which includes currency and checkable deposits but not bank certificates of deposit (CDs), has been growing at about a 7 percent annual rate in the past three months or six months. Alan Meltzer, a prominent monetary economist at Carnegie-Mellon University, reckons that's enough M1 growth to permit 5 to 6 percent nominal growth in the next 12 months, 2.5 to 3 percent real growth, and 2.5 to 3 percent inflation. He explains the divergence between M1 and M2 as being the result of a sharp drop in short-term interest rates. Owners of CDs are reluctant to renew them and tie up their money for months or years ahead at those low rates when they can get almost as good an interest rate in checkable deposits. So billions of those dollars are being invested in money market funds, bond funds, or elsewhere in the economy where a portion of it may not show up in the money supply. "We never know precisely these things in such a complicated economy," says Dr. Meltzer. Another Wall Street economist, Robert Parks, notes that when CD money moves into checkable accounts, banks must lay aside 12 percent of that money as reserves with the Fed. So, despite a rapid increase in bank reserves, the Fed is actually carrying out a "stringent" monetary policy, he maintains. This could prompt an "economic relapse" of recession. Michael Keran, chief economist of Prudential Insurance Co. of America, notes a related phenomenon: the commercial banks' share of the market for credit is shrinking. They are losing out to finance companies, commercial paper, money market funds, bond funds, etc. So they have less need for or are unwilling to compete so hard for CD money. That also tends to shrink M2. However, Mr. Keran regards M1 as the most important measure of money, since cash and checking deposits are the primary means of making payments, directly or indirectly. He expects real growth next year to amount to 3 percent - not a "huge recovery." Under chairman Alan Greenspan, the Fed has been far steadier in supplying reserves to banks than under his predecessor, Paul Volcker. The White House probably thinks that's a good idea theoretically - but not now. It wants more credit ease.