Of course the world is not in perfect balance, and there are ideological reasons that explain why one party would engage in unethical actions more often than the other to achieve political goals. For example, if one party ascribes to the belief that the ends justifies the means, while the other party believes that moral ends cannot be achieved by immoral means, there will naturally be more political shenanigans perpetrated by members of the former party.
One of the most striking imbalances in modern U.S. politics is that between the more extreme wings of the two major parties. While Republicans will fight with each other over who is the stronger and purer conservative, Democrats will generally play to the middle. The word "liberal" was all but excised from the vocabulary of Democrats back during the Bush Sr. Dukakis race. One of Bush's strategies was to accuse Dukakis of being a liberal, as if to equate the word with "communist." Near the end of the race, under pressure from his supporters, Dukakis tried to recapture the positive connotations of the word "liberal," but by then it was too late. Now, if you hear the word "liberal," it's mostly used as an accusation by "proud, strong" conservatives. Politicians on the left have opted for the less tainted "progressive" to describe themselves.
In 2010, this imbalance proud conservatives vs. embarrassed liberals is more extreme than ever. We have been witnessing a string of primary defeats of traditional conservative Republicans by more extreme Tea Party backed Republicans. On the other hand, progressive Democratic challengers have not yet been able to displace many moderate (conservative by yesterday's standards) Democrats. One could say that this bodes well for the Democrats in a general election because it indicates that the Democratic base is happier with their incumbents than the Republican base and that the Republicans are fielding candidates so extreme in their politics that they are unlikely to garner much support in the middle. That would be a reading of the situation that is pretty generous to Democrats. Another reading is that Democrats are making the same mistake they make perennially, of trying in vain to get moderate Republicans to vote for them by watering down their stands on issues, while the Republicans are recreating themselves as a party that clearly stands for a set of principles.
Perhaps one of the most telling signs of the imbalance in attitudes that Democrats and Republicans have about political strategy, is that an endorsement from right-wing politician and failed Vice Presidential candidate Sarah Palin is sought after and valued while no Democratic candidate would care for the endorsement of one of the most progressive members of Congress (and failed Presidential candidate) Dennis Kucinich.
It is frustrating for progressives who are not politicians to watch all this going on. It appears that Democrats cede the terms of the debate on nearly all issues to the Republicans, which puts them on the defensive, and are even shy about holding strong progressive (or, dare I say "liberal") views. This gives the Democrats very little to run on they already used up the "We are not George Bush" campaign strategy, promising ill-defined "change." That was a winner in '08. But now the Republicans are redefining themselves as a party that is not George Bush either it's further to the right. If Democrats would just step back and remember that the vast majority of Americans agree with them on all of the major core issues of their party's platform, they could run as proud, strong liberals instead of as scared, embarrassed fake-conservatives.