The most popular theory is that Cain's departure would hurt Mitt Romney and benefit his chief rival at the moment, Newt Gingrich. The GOP electorate maintains severe reservations about Romney, so his strategy for winning has always depended on squeaking through as conservatives fail to settle on one alternative. If Cain were to leave, there would be one less candidate to carve up the conservative vote, thus complicating Romney's strategy. Though Cain has declined in polls over the last several weeks, according to the Real Clear Politics average, he's still at 15.5 percent nationally, 15.8 percent in Iowa, 7 percent in New Hampshire and 16.7 percent in South Carolina. Gingrich has been the beneficiary of Cain's recent slide, and would theoretically stand to gain ground if he were to drop out.

Yet there's also another way of looking at things that could play into Romney's hands. If Cain does end up dropping out over reports that he had an affair, it could lead to a greater focus on Gingrich's messy personal life, three marriages and extra-marital affair. Though Romney is unlikely to directly attack Gingrich on this, expect to hear a lot more about Romney's 42-year marraige to emphasize that this isn't an issue Republicans would have to worry about should he be the nominee.