What? Barack Obama just creamed John McCain in the nationwide popular vote, but McCain prevails because he won in the Electoral College?

What? California went for a Republican for the first time since 1988, giving McCain a decisive 55 electoral votes?

Neither scenario is implausible. The referendum in California to reverse a state Supreme Court ruling in favor of gay marriage seems certain to bring out hundreds of thousands of conservative voters. And if enough irate Hillary Clinton voters carry out their threats to sit out the election or even vote for McCain, ol’ Mac would be in clover.

Some bloggers already are calculating that McCain could lose the popular vote and still win the presidency. That scenario, with its echoes of 2000, should be motive enough for our Legislature to pass a National Popular Vote bill. It was approved in committee last fall but has lingered on the House calendar for months.

The bill, advocated by Common Cause, would commit Massachusetts, in a binding compact with other states, to cast all its electoral votes for the winner of the nationwide popular vote. Once enough states totalling the 270 electoral vote majority sign on, the popular vote system is in place. And that would be good for both parties, especially in Massachusetts and in other hard-core blue or red states:

This year, your vote, whether you’re for the Democrat or the Republican, won’t matter much. The Democratic nominee is almost as sure to win Massachusetts as the sun is to rise tomorrow. There’ll be little campaigning here, or in other such “safe states.”

But if the popular vote system were in place, you Republicans wouldn’t have wasted your vote. You’d be building up your candidate’s national total and staving off the kind of fate President Bush almost suffered in 2004 when a shift of only 60,000 Ohio votes would have madeJohn Kerry the Electoral College winner, despite Bush’s 3.5 million edge in the popular vote.

And you Democrats could avoid a repeat of the fury-in-Florida finale of the 2000 Bush-Gore race, dramatized this week in HBO’s “Recount.”

Small states would be helped, not marginalized, by the popular vote approach. Maine, Rhode Island, Montana and the like usually vote heavily for one party and get taken for granted by everybody.

In Massachusetts, Senate President Therese Murray has endorsed the bill and promises to move it through the Senate as soon as the House acts. A spokesman for Sal DiMasi said yesterday that the speaker is taking a serious look at the issue. House Election Law Committee Chairman Garrett Bradley, who defends the bill passionately, said “It’s been held up because some members wanted to see how it’s doing in other states.”

Pretty well, said Barry Fadem of the National Popular Vote Campaign, who has been lobbying in Massachusetts and North Carolina, whose total of 27 electoral votes would add heft to the four states with 50 electoral votes which have already passed it.

That would make 77 electoral votes, with Illinois, New Jersey, Maryland and Hawaii on board and with 17 state legislative chambers having passed it. If Massachusetts and North Carolina come on this year - pushing the count close to a third of the 270 electoral votes needed - “We can get this done in 2010,” Fadem said.

Another sponsor, Rep. Marty Walsh of Dorchester, said, “We’re preaching democracy all over the world, but our voting doesn’t always reflect that . . . We have a chance to make sure the vote of every man and woman counts.”

Indeed they should. And Massachusetts - long a leader on many causes - should show the way on this one, too.