(MCT) — WASHINGTON — Congress returned from its election break Tuesday to grapple with the shocking resignation of former CIA Director David Petraeus in a sex scandal that widened to possibly taint the Marine general who commands U.S.-led forces in Afghanistan.

The unexpected turn of events prompted President Barack Obama to put on hold his nomination of Marine Gen. John Allen to be the top NATO commander in Europe, pending the outcome of a Pentagon investigation into “inappropriate” emails that U.S. defense officials said Allen had sent to a central figure in the scandal, which was ignited by Petraeus’ admission to an extramarital affair.