Two weeks ago, I directed readers to an analysis by Keith Poole of UC San Diego on the relative ideological positioning of the three main candidates for President. Poole provides an excellent analysis of Congressional voting patterns called the Poole Report, which provides the broadest basis used for rating members of both the House and the Senate. The Poole Reports use roll call votes that have at least 0.5% of members voting in the minority. For example, the 2007 session of the Senate had 388 data points, as opposed to the ACU’s 25 and 107 for the National Journal, which gives a much more complete look at the partisan nature of voting for both Republicans and Democrats.

Poole’s analysis shows a fascinating and perhaps disturbing trend. Despite the perceptions of many in and out of the blogosphere and punditry, the parties have moved away from compromise, not towards it. Poole’s charting of partisan voting behavior over the last 40 years makes this plain:

Note the progression of the voting pattern, and where today’s candidates would have scored on this timeline with their 2008 positioning. In 1968, McCain would have been on the right wing of the Republican Party, and both Obama and Clinton would have been significantly on the left side of the Democrats. By 1988, McCain exists squarely in the GOP’s mainstream, and both Obama and Clinton remain on the left wing of the Democrats. Now, McCain’s fixed 2008 position puts him on the moderate side of the party, while the mainstream of Democrats have just barely reached Obama and Clinton’s position.

Now re-run the animation and look at what happened to the center in American politics. Forty years ago, members in both parties routinely overlapped, and their mainstreams existed closer to the center. The crossover point came just to the right of center and about halfway to the peak of both parties. In 1988, the crossover point hit about the same spot but much lower on the density scale, and the overlaps of both parties extended much less into the density of the opposition. Now, there is almost no density at the crossover point and the overlap has all but disappeared entirely.

What does this mean? It shows that RINOs and DINOs exist largely as mythology. Congress has become a place where party-line votes prevail on an almost-exclusive basis. Those who believe that we lose elections because of a lack of party discipline and loyalty in the legislature have targeted the wrong culprit. Neither party has a lack of discipline, but both may have allowed a critical gap to open with the American electorate that could threaten the two-party system.

Much has been made of independent runs from Bob Barr, Ron Paul, and Ralph Nader, but this shows that they also miss the point. The opportunity for political traction doesn’t come from the extremes of the Left and Right, but from the center. At least in Congress, both parties have abandoned American voters in the center, and are to this day still trending away from them. This could be the greatest opportunity in decades for a real third party to form and represent the gap that the last 40 years has opened between the parties. That opportunity will not be realized at the presidential level, but rather in the House and Senate.

This gap does have meaning in the presidential race. Even though Republicans have many structural problems in this election, they may have nominated the one man who can actually engage the center better than any of the two dozen candidates who ran in this cycle’s primaries in both parties. Not only does McCain occupy a spot on the spectrum closer to the center than anyone else, he’s also perceived to be more centrist. He has a track record of independence in his voting record that frankly is almost nonexistent in today’s politics. While that certainly (and legitimately) frustrates conservatives, it speaks to a wide range of American voters who find themselves lost in a deepening and widening valley between two peaks.

If McCain can capitalize on that and can find messages that resonate with those voters — and especially if he can demonstrate the hard-Left credentials of his opponents — he may find a treasure trove of support in a year where Republicans elsewhere are likely to take a beating.