President Obama won the popular presidential vote in November by slightly less than five million votes: The president received about 65.9 million votes to Mitt Romney's 60.9 million. Of course, it's not the popular vote that matters, as 2000 popular vote winner Al Gore could tell you. It's electoral votes that decide who becomes president.

Mr. Obama's electoral vote victory was actually significantly larger than his 3.9 percentage point popular vote advantage: He took 332 electoral votes to 206 for Romney. Why the disparity? In part because of the way electoral votes are allocated. Most states allocate their electoral votes based on who wins the popular vote: Even though Mr. Obama only won Florida narrowly in November, for instance, he got all 29 of its electoral votes.

There are two states that do things differently. In Nebraska and Maine, electoral votes are allocated based on who wins each congressional district. That means that the winner of the statewide popular vote doesn't necessarily get all of a state's electoral votes - or even the majority of them.

The allocation system used by Nebraska and Maine has never been seen as a big deal, because neither state plays a very big role in deciding the president. (Between them, they only controlled nine electoral votes in 2012.) But a push by Republicans in some crucial swing states to adopt the system used in those two small states has Democrats accusing the GOP of effectively plotting to steal the next presidential election.

Republican lawmakers in at least five big states that went to Mr. Obama in November have floated measures to allocate electoral votes based on the outcome in congressional districts: Virginia, Ohio, Michigan, Wisconsin and Pennsylvania. In Virginia, a bill to shift to such a system goes to a state senate committee on Tuesday. State Sen. Charles W. Carrico Sr., who sponsored the bill, told the Washington Post that it would mean that smaller, non-urban communities would have more say in the presidential election. "The last election, constituents were concerned that it didn't matter what they did, that more densely populated areas were going to outvote them," he said. (In Carrico's bill, the state's two at-large electors would go to whoever wins the most congressional districts.)

Mr. Obama won four districts in Virginia in 2012. Romney won seven. Under Carrico's plan, Romney would have taken nine of Virginia's 13 electoral votes, while Mr. Obama would have taken just four - despite winning the statewide vote by almost 150,000 votes. This is due in large part to the fact that Romney won most of his districts relatively narrowly - he took more than 60 percent of the vote in just one of them - while Mr. Obama won his districts by large margin, taking at least 60 percent of the vote in three of his four districts.

"It's sore losers, it's a sore losers bill," said Virginia Democratic state senator and former gubernatorial candidate Creigh Deeds. "We're going to do everything we can to defeat it."