You're absolutely correct that a third party vote will have no say on which of the two major party candidates wins -- a third party vote is entirely neutral, favoring neither Coke nor Pepsi.
However, enough third party votes to force a plurality win would be very far from symbolic. It would have solid effect on the power dynamics of the victor, just as it did in 1992 when third party votes forced a 43% plurality for Bill Clinton, who was opposed by a full 57% of American voters, and consequently got his butt kicked in the midterms with the Republican Revolution. If he had won with a majority (or if HW had been re-elected), that Republican Revolution would probably never have happened.
No, the "pretending" is being done by those who think they're voting "against" Obama instead of voting for Romney.
Six months, one year, into a Romney presidency, as Romney quietly, firmly, blithely snubbed conservative Republicans and with the help of moderate Republicans, the GOP-E, and Democrats steadily, forcefully advanced all of the major liberal agendas as he did while Governor of Massachusetts, and while the conservatives we all voted for so diligently down-ticket became impotent to fight Romney's agenda, all the ABOers would be sputtering ....
....."B-b-b-b-b-b-but ... we didn't vote for this! We were voting against Obama, not for Romney and all his progressivism!"
No, you were only pretending to. No matter how you rationalize it or what your actual intentions are, a vote for Romney is a vote for advancing liberalism and big government statism on the back of the Republican party and weakening conservatives. That is what your vote "against" Obama is FOR.
The hard cold reality is that no one can really vote "against" Obama or Romney, and that one of the two is going to be the next president. But you CAN vote to make whichever guy wins as weak as possible in office, not "symbolically," but tangibly.
If one in three voters -- Democrat, Republican, Independendent, Libertarian, whatever -- is disgusted enough with the Obama vs Obamalite charade and votes third party, it will be ON RECORD that in the popular vote, two in three voters REJECTED the sitting President, and that fact -- not symbol, dirtboy, but FACT -- will make him vulnerable to his enemies within and without, weak, defensive, humiliated, and a mockery in the public eye.
He would be put on the defensive. Considering that it would be happening to a president who is anti-conservative and pro big-government in any case, that would be a GOOD THING.
A Romney landslide, on the otherhand, which fear-motivated ABO risks, would be something every ABOer would come to regret with extreme anguish.
Panic and hysteria have always made people do stupid things. I hope American voters realize that in time to avoid a Romney landslide.
I don't see that happening, either, quite frankly. Dissent with both major candidates might be able to reach ten percent, but we are not seeing anything close to that in the polling. Plus, only winning with a plurality didn't slow Clinton down his first two years.