Richard Rountree once trusted the government and voted for Democrats. These days, however, the 55-year-old owner of an Internet technology company who lives in Azalia, Mich., does neither.

"I'm frustrated," he says. "I think a lot of people are."

Rountree's journey –– from a ticket-splitting youngster with faith in the system to a staunch conservative who contends "the other side just seems to be so full of it" –– suggests he could be the face for a statistical portrait of America's voters 50 and older. For much of his life, he says, he paid little attention to how politicians governed, "because, for the most part, you could trust the people you sent to Washington."

But after starting his business in 1996, Rountree says, he became alarmed by the growth of government spending. He also became alarmed at how politicians in both parties constantly broke their promises to curb spending. Now, he says, he knows when politicians are lying: "Their lips are moving."

Here are four reasons why incumbents will be thinking about voters like Rountree as the 2010 midterm elections approach.

1. Anger. This emotion was reflected in a Pew Research Center/National Journal poll, released in May, in which one-third of 50-plus Americans said they were less likely to vote for an incumbent, compared with just 13 percent of those who are ages 18 to 29. On the flip side, about 30 percent of 50-plus Americans said they were more likely to vote for someone who has never held elected office, twice the rate of the youngest voters.

Some analysts say the one-two punch of a health care debate that prompted questions about the viability of Medicare and an economic slump that devalued retirement accounts and cost older workers their jobs fuels the discontent. "It may be that seniors are experiencing a sense of vulnerability, a sense of uncertainty," says Paul Freedman, a political science professor at the University of Virginia in Charlottesville.

Ross Baker, a professor of political science at Rutgers University in New Jersey, says that when he spoke about politics at an assisted-living facility in New Jersey, he "had not reckoned on the level of hostility toward government. They feel their security is under attack. They're very much into blaming, and they blame the incumbents."