The proportional vote and the Maine-Nebraska method are completely different systems.
http://en.wikipedia.org/wiki/United_States_Electoral_College#Reform_proposals
Proportional vote
The primary proposal of this type is for states to implement a proportional vote system. Under such a system, electors would be selected in proportion to the votes cast for their candidate or party, rather than being selected to represent only the plurality vote. As an example, consider the 2000 election, in which the George W. Bush / Richard Cheney (Republican) and Albert Gore Jr. / Joseph Lieberman (Democrat) tickets were the primary contenders, with the Ralph Nader / Winona LaDuke (Green) ticket taking a small but noteworthy minority. In California, the approximate proportion of votes for these tickets was 41.65 percent Bush/Cheney, 53.45 percent Gore/Lieberman, and 3.82 percent Nader/LaDuke. Under the current system, all 54 electoral votes were for Gore/Lieberman. Under a simple proportional system, the votes might be distributed as 23 Bush/Cheney, 29 Gore/Lieberman, and 2 Nader/LaDuke.
As a practical matter, this system would be very difficult to implement. According to the Constitution, the state legislatures decide how electors are chosen. It is usually not in the interest of an individual state to switch to a method of proportional allocation because it reduces that state's influence in the Electoral College. This can be illustrated by the case of Colorado, which in 2004 voted down an initiative on its 2004 ballot, Amendment 36, which would have instituted a system of proportional allocation of electors beginning immediately with the 2004 election. Had the proposal passed, Colorado would not have been a swing state in 2008, no matter how closely contested. The state's nine electoral votes would almost certainly end up divided 5-4, no matter which candidate won a plurality. Thus, winning the Colorado popular vote would only give the successful candidate one additional electoral vote over his or her opponent instead of nine.
A perceived problem with dividing electoral votes proportionally is that it would be harder for a candidate to achieve a majority of the electoral vote, since a proportional system would enable a third party candidate to win electoral votes. If this system had been used in 1992 and 1996, and all electors had voted as pledged, there would have been no winner at all, and the House of Representatives would have chosen the president, and the Senate would have selected the Vice President. In 1996 Robert Dole would almost certainly have been the House winner, and Jack Kemp the Senate winner, despite receiving significantly fewer votes than Bill Clinton and Al Gore. In 2000, Al Gore would have received 269 electoral votes, George W. Bush 263, and Ralph Nader 6. If all electors voted as pledged, the Presidential race would have gone to the House, and Bush likely would have won, but the Vice Presidential decision in the Senate would have likely split 50–50 for Lieberman, with Al Gore (as then-president of the Senate) casting the deciding vote.[citation needed]
[edit] Maine–Nebraska method
Other observers argue that the current electoral rules of Maine and Nebraska should be extended nationwide. As previously noted, the winner in each of those two states is only guaranteed two of Maine's four and Nebraska's five electoral votes, with the winner of each Congressional district in those states receiving one electoral vote. Using the California example again, Gore won 33 of the state's Congressional districts and the state overall, while Bush won 19 Congressional districts. The state's electoral votes would then have gone 35–19 for Gore.
However, this kind of allocation would still make it possible for the loser of the popular vote to become president.
Dividing electoral votes by House district winners would create yet another incentive for partisan gerrymandering.
Another perceived problem with this suggestion is that it would actually further increase the advantage of small states. In winner-take-all, the small states' disproportionately high number of electors is partially offset by the fact that large states with their big electoral blocks are such a highly desirable boon to a candidate that large swing states actually receive much more attention during the campaign than smaller states. In proportional representation or Maine–Nebraska, this advantage of the large states would be gone.
Yet another argument with both Maine–Nebraska and proportional representation is that even if it is considered superior as a nationwide system, winner-take-all generally maximizes the power of an individual state and thus while it might be in the interest of the nation, it is not in the interest of the state to adopt any other system. Since the United States constitution gives the states the power to choose their method of appointing the electors, nationwide Maine–Nebraska without a constitutional amendment mandating it seems unlikely, and the passage of such an amendment seems equally unlikely since the House delegations of the largest states (against whose interests such a system would be), taken together, easily surpass the one third of the House size that is needed to block a constitutional amendment.