I think it's highly likely that Gavin had such a broad effect on the election and even helped shift the country to the right. Sometimes standing up for principles you believe in can have that effect, though the Democrats shouldn't blame the guy (unless they thought his actions were wrong to being with). If everything was on such a razor edge that simply causing a rally to arms around a single issue can cause such a shift, then it was bound to happen and some other minor effect could have caused the same result. His actions could have just as easily gone the other direction.

And really, this guy didn't necessarily change what the people of the US believed, he only caused them to reveal it a bit more than perhaps they would have.

Finally, who knows what the long-term effect will be. Maybe Bush will decide to invade France and then we'll get an even bigger shift to the left in retaliation. . .