John Brunner meets with supporters after announcing his candidacy for U.S. Senate in October. (Jeff Roberson/AP)

Beginning Tuesday night, a series of GOP Senate primaries offers the latest test for a specific type of political species that has had mixed results over the past few decades: the businessman-outsider-turned-candidate.

In Missouri, Wisconsin and Arizona, a trio of wealthy businessmen have tapped their own bank accounts to surge near the lead of Republican primary contests this month by portraying themselves as anti-politicians ready to come to Washington to fix things.

It’s an age-old phenomenon that has had hits shares of highs (Sen. Ronald H. Johnson, a Wisconsin Republican, stormed from virtually nowhere to oust three-term Democratic Sen. Russell Feingold in 2010) and lows (former Hewlett Packard chief executive Carly Fiorina lost decisively to Democratic Sen. Barbara Boxer that same year in California’s race). It’s also being put to the test in the presidential campaign, as GOP nominee-in-waiting Mitt Romney has built as the cornerstone of his campaign his service as the head of private equity firm Bain Capital.

The first contest is Tuesday in Missouri, where manufacturing executive John Brunner is in a tightly contested three-way primary that has split the conservative coalition and its interest groups into competing corners. By late July, Brunner had spent more than $7.5 million of his own money to push ahead of a pair of conservative politicians, Rep. Todd Akin (Mo.) and former state treasurer Sarah Steelman.

Next week in Wisconsin, hedge fund chief Eric Hovde, with the help of nearly $5 million of his wealth, is in another three-way battle, this one against former governor Tommy Thompson and former congressman Mark Neumann. And in Arizona, real estate investor Wil Cardon has turned what many thought would be a coronation for Rep. Jeff Flake by pouring more than $7.5 million into his effort to portray the six-term congressman as an insider — despite his years of clashing with his own leadership over spending issues.

In launching these campaigns, the wealthy businessmen are trying to tap into the general disgust many voters have for Congress, which has an approval rating just above 15 percent in most recent public polls. Running as outsiders keeps the taint off their candidacies, enabling them to state — as Brunner does in his commercials — “the career politicians are crippling America.”

“I think that the biggest attraction of these candidates is that they have been outside the political process and have been successful,” said Jennifer Duffy, the senior editor for the independent Cook Political Report.

However, according to a Washington Post analysis, over the past four elections, only six senators have been elected without previously holding some kind of elected position, and Johnson is the only one to come directly from the business world. Before that, New Jersey Democrat Jon S. Corzine, after leaving Goldman Sachs, was the most recent businessman-outsider to come straight from the corporate world to the Senate, having spent more than $60 million of his own money to win his 2000 race.

Duffy warned that the public has different views for different sorts of businessmen. Johnson runs a manufacturing plant in Wisconsin and used his plain-spoken ways to poke fun at Washington in his campaign, often turning to a basic whiteboard to relate to voters. Brunner, who has the endorsement of the U.S. Chamber of Commerce, runs a family-owned personal-care products business near St. Louis.

“There are the Ron Johnsons and John Brunners, who made money making things,” she said. “Their businesses were local and part of the community, or at least had a local feel to them. I think voters have a harder time understanding how a Hovde or a Romney made money.”

Hovde, before returning to Wisconsin after more than two decades running a fund in Washington, faces a similar hurdle as Romney in explaining to voters how he made his millions through investing in other companies and funds. As Hovde has spent freely in attacking Thompson as an establishment figure, Neumann has picked up steam in recent polls with the backing of prominent conservative figures such as Sen. Tom Coburn (Okla.).

As president of the Cardon Group, Cardon tries to focus his effort in explaining his family business, described by its Web site as a “diversified holding company,” as “creating jobs, investing in people, products, properties, and helping start-up companies succeed.”

Sometimes, business backgrounds offer ripe targets, leading Flake to highlight arrests of illegal immigrants at sandwich shops that Cardon’s diverse firm owns.