Disappearing jobs, burrowing consumers and skittish companies are reasons for the Federal Reserve to lower interest rates and brace the tottering economy.

Fed Chairman Ben Bernanke and his colleagues open a two-day meeting Tuesday afternoon — their last before the November elections — to make a fresh assessment of economic and financial conditions and decide their next move on rates. Their decision will be announced Wednesday.

It is all but certain the Fed will cut rates — for the second time in this month alone. The big question: Just how low will the Fed go?

Investors on Wall Street and many economists are betting the Fed will slash its key rate by half percentage point to 1 percent. A few, however, however, think the Fed will opt for a smaller, quarter-point reduction to 1.25 percent.