One thing we keep hearing from the average, passive political observer is that 'both sides are the same' and that it 'doesn't really matter who we elect.' As much as I hate to admit it, I have found difficulty in arguing against that, but I believe that is because the Democrats have surged so far to the right that and have become rather complacent about the things that they do claim to believe in. No matter what we do in other words the Republicans find a way to win but I had a hard time explaining exactly HOW to explain the difference between the Democrats and Republicans on the old left-right axis.
What I came up with was a simple, common sense way to put it; compare the two major parties to the third parties that associate themselves with the bigger brothers. On the left side, the largest third party around is the Green Party which is far to the left of the Democratic Party. Other left wing leaning parties tend to have the word communism or socialism in their names and are far to the left of the Democratic Party and as I look around I can't seem to find a third party that is left leaning but to the left of the Democrats.
On the other side, the biggest third party associated with Republican politics is the Libertarian Party. On economic issues they are around the same as the Republicans but on social issues...they support removing any laws restricting homosexuality, they wish to end the drug war, and refuse to take a stance on abortion issues which are generally considered 'liberal' positions by the public at large. It means that the 'crazy-right winger' libertarians are actually to the left of the GOP to some extent. The few parties to the right of the Republicans (Constitution Party, America First Party) aren't that far to the right of the GOP. So even the most active extremists can't get very far from the Republican Party's official stance.
In short, the radical left wing is far to the left of the Democratic Party. The Radical right wing is not very far away, and sometimes even to the left of the GOP.