(CBS NEWS) -- 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."

Emory University political science professor Alan Abramowitz, who considers the Carrico proposal and those like it to be "profoundly undemocratic" because it skews election results toward the party that has drawn gerrymandered congressional districts, found that if all states had allocated electoral votes in 2012 by congressional district, Romney would have taken 276 electoral votes (and with them the presidency) to Mr. Obama's 262 electoral votes. That's despite Mr. Obama's nearly 5 million vote advantage in the popular vote. (Abramowitz' calculation was based on the notion that the two at-large electors would go to the statewide popular vote winner, not whoever won the most congressional districts.)

According to Abramowitz, Romney would have won 12 out of 18 electoral votes in Ohio, nine out of 16 electoral votes in Michigan, 12 out of 20 electoral votes in Pennsylvania, and five out of 10 electoral votes in Wisconsin - despite losing all four states, in some cases by large margins. (Because of incomplete data, he had to estimate from previous data in some Pennsylvania districts.) 

It's no coincidence that the states where Republicans are pushing proposals to shift to allocation based on congressional districts were all won by Mr. Obama in November - but are controlled by Republicans on a statewide level. 

Reince Priebus, the newly reelected chair of the Republican National Committee, said Friday that while such efforts are a "state issue," he is "pretty intrigued by it" and believes "in some cases they should look at it." 

In Michigan, Rep. Pete Lund, a Republican who plans to introduce a bill soon, told the Detroit News that it would make the system "more representative of the people -- closer to the actual vote." Lund, who introduced a similar measure last year, added that part of the reason it did not get traction lat time is that there "were people convinced Romney was going to win and this might take (electoral) votes from him."

It's not clear just how far these proposals will get this time around: The Virginia plan may well not get out of committee, since two Republican state senators on the committee on record as opposing it. Even if it does clear the legislature, a spokesman for Gov. Bob McDonnell, R-Va., said Friday he would oppose the measure.

Similar measures have been introduced in the past and failed to get anywhere - and it's worth noting that it hasn't always been by Republicans. As Deeds acknowledged, Virginia Democrats pushed similar bills back when they were regularly losing the state of a presidential level. 

Opponents to such proposals point out that moving to such a system would have the effect of making the candidates far less interested in campaigning in what had previously been swing states - depriving the state of millions of dollars that would have otherwise flowed in during the campaign.

Rob Richie, executive director of the nonprofit electoral reform group FairVote, said that moving to a system of allocation based on congressional district would shift candidates' focus of to suburban districts, since those are the ones that tend to be competitive. 

"The presidency would be decided not in America, but suburban America," he said. Richie, who advocates a system by which states agree to allocate their electoral votes to the national popular vote winner, called the proposals "the wrong fix for a real problem."

"It doesn't fix what's really broken about our current system," he said. "And added to that, has incredibly indefensible partisan consequences." A Gallup survey taken earlier this month found that 63 percent of Americans, including more than six in 10 Republicans, Democrats and independents, support "doing away with the Electoral College and basing the election of the president on the total vote cast throughout the nation."

Were the changes to get passed and signed into law, they could face legal challenges. Columbia University election law expert Nathaniel Persily said the Virginia law could potentially be challenged under the Voting Rights Act, with an argument that the move discriminates against African-Americans. He added that it could be challenged in any state with a claim that it violates the equal protection clause of the 14th amendment, and could also be challenged under the constitutions of the various states.

Persily acknowledged, however, that the courts have not struck down the system in the two states where it is already in place. 

"You have to think of a legal theory that would strike this down but not strike down Maine and Nebraska," said Persily. "The question is, does the motivation make a difference?" He said the motivation argument could be made in the context of other recent moves by Republicans, including the voter ID and early vote changes seemingly designed to boost the GOP.

No matter how it played out, he added, passage of such laws would be "tantamount to a declaration of political nuclear war."