"The critical question is, if he wins, when does he announce it?" said El-Erian, who serves as co-chief investment officer with Pimco founder Bill Gross. "It turns Chairman Bernanke into a lame duck the minute that announcement is made."
The Fed has sought to drive down unemployment by keeping its target rate for overnight loans between banks between zero and 0.25 percent since December 2008 and purchasing $2.3 trillion of securities in two rounds of a monetary policy known as quantitative easing.
Frustrated by the slow pace of the recovery, the Fed announced Sept. 13 that it would likely keep rates at a record low and also said it would inject more money into the economy by purchasing $40 billion of mortgage bonds per month in a third round of QE until the jobs shows "sustained improvement."
Pimco, a unit of the Munich-based insurer Allianz SE, managed $1.82 trillion of assets as of June 30.