From Mother Jones: the GOP in Pennsylvania (which controls the legislature and the governorship) is pushing a scheme to allocate all but two of the state's electoral votes on the basis of which presidential candidate wins in each of the state's congressional districts. Other large GOP-controlled states may follow their lead as well. This scheme is likely to produce perverse outcomes, with a candidate conceivably winning the popular vote in a large state like Pennsylvania, while receiving less than half of its electoral votes. Currently this scheme is used only in Maine and Nebraska, where the small number of congressional districts renders the whole question less important.
For reference, remember that in the 2000 election, Gore beat Bush in the national popular vote by 48.4% to 47.9%, while losing the electoral vote by 266 to 271 (49.4% to 50.4%). If the congressional district method had been used, we can see here that Gore would have won only 238 electoral votes (195+(2*20)+3) or 44.2%, while Bush would have won 300 electoral votes (240+(2*30)) or 55.8% - a result more perverse than what really happened.