Many people looking at my headline would immediately assume those two concepts -- centrism, and swing voters -- have a direct and exceedingly close tie to each other. And in some ways, in some elections, at some times, they certainly have. But the connection is growing more and more tenuous, which is why centrists like Dede Scozzafava are far from the first or last to have to face defeat. Two closely related dynamics drive the political reality here.
The first is that for all the attempts by DC elites in both parties to kill it, an anti-establishment populism is alive and well in this country -- and is in fact probably stronger than it's been at any time since the 1930s. With the economy still causing people incredibly high levels of pain, with Wall Street bankers destroying the economy yet getting bailed out and making more money than ever, with big corporate lobbyists still having way too much power no matter which party is running things, middle and working class voters are angry and cynical at politicians in both parties. That kind of anger has a left and a right wing version, but in general it doesn't lead to party insiders being trusted to handpick candidates, and it doesn't lead to careful, cautious incumbents being automatically re-elected.
The other dynamic is that centrism itself, at least as it is practiced in DC, has become a corrupted term. I can think of several different kinds of people in the real world outside of DC that I could comfortably define as centrists, including fiscal conservatives wary of deficit spending but who are open to new ways of re-structuring government and are genuinely compassionate about people suffering; working class populists who believe in taking on big business but are nervous about moving too fast on social issues; suburban professionals who are nervous about higher taxes but pretty liberal on social issues; working class Hispanics whose Catholic faith is dear to them but whose families sometimes need government help, and who are upset by the race baiting they see on the immigration debate; young people still trying to get established in a career track, and not even very sure politics or government matters very much to them; working class women worried about taking care of their kids and paying the bills who aren't sure government is doing anything that matters in their lives; libertarians who don't like anything that is too big or too powerful, whether it's government, corporations, or powerful churches trying to dictate to everyone how to live their lives.
All of these kinds of people and more could be categorized to one extent or the other as centrist, and many of them are swing voters. But in DC, "centrism" almost always seems to boil down to be in favor of big corporate interests. The "centrists" on health care don't want a public option because it might hurt the insurance industry, they like the deal with the drug companies that keeps the government from saving money by negotiating drug prices, and they don't want big business to be responsible for contributing to insuring their workers. The "centrists" on banking issues don't want to break up the too big to fail banks, or impose a consumer safety regulator on them, or keep banks from trading in derivatives. The "centrists" on climate change don't want to impose new regulations on oil or coal companies.
It's almost impossible to name a major economic issue where the Blue Dogs and centrist Democrats in the Senate are not working directly and closely with corporate lobbyists. That is the case even though the constituents of most of those Blue Dogs tend to be poorer and more exploited by those big businesses than the average American, and even though on many issues siding with those big business lobbyists is far worse in terms of the federal budget that these Blue Dogs always say they are worried about (see the public option, or negotiating with drug companies, or in fact most of the issues mentioned above).
The bottom is falling out of the foundation for establishment centrism in this country. Voters of all stripes are angry and cynical about the political establishment in this country, and the politicians and pundits who claim to be centrists have all too often simply become flag carriers for the corporate lobbyists who fund their campaigns. The rise of populist movements in both the Republican and Democratic parties has flowed from these powerful political dynamics, and I hope my party, the Democrats, come to understand and respond to that in time.