Mississippi voters can help their state's economy this Tuesday by sending Sen. Thad Cochran into retirement.

Cochran, in a runoff for the Republican nomination to hold his seat, is one of the Senate's legendary porkers. He was the upper chamber’s most prolific purveyor of earmarks every year from 2008 (when Sen. Ted Stevens was indicted) through 2010, when the Republicans banned earmarks, over Cochran's objections.

'They're still spending money. Money is going out every month and nothing is being done.'

Cochran still has disproportionate control over Congress’s purse strings. He is the ranking member of the Defense Appropriations subcommittee, and if he’s reelected and Republicans take control of the Senate, Cochran will chair the full Appropriations Committee. He’s also a senior member of the Agriculture Committee.

These perches allow Cochran to send money back to Mississippi, and that’s been a core message of his campaign.

“Over the years, we've had to fight for funds” for Mississippi ports, companies, and military bases, former Mississippi Sen. Trent Lott says in one recent Cochran ad. “Without Thad Cochran we could lose some of these important facilities.”

Haley Barbour, the former Mississippi governor, has promoted Cochran using a similar argument, stressing “how much he has helped and can continue to help Mississippi.”

Given how much federal money Cochran has brought back to the state, why is he struggling? Why did the incumbent finish second in his June 3 primary? Why is he tied or trailing badly in the polls taken during the runoff?

Maybe it's because federal largesse doesn’t help the regular people back home as much as Washington tends to assume.

Having your senator become Appropriations Chairman appears to “significantly dampen corporate sector investment and employment activity,” a 2010 study by three Harvard Business School professors found.

The study, published in 2010 by the National Bureau of Economic Research, explored whether federal aid helped or hurt a district or state. One difficulty in exploring this question: Poorer areas might tend to attract more federal dollars, thus skewing the data.

So the scholars used an innovative way of measuring the impact of federal money: Since a state gets much more in federal funding when its lawmaker gets a committee chairmanship, how does that state’s economy perform during these gavel-induced floods of federal cash?

Not well, it turns out. The federal money crowds out private investment, and “In the year that follows a congressman’s ascendency, the average firm in his state cuts back capital expenditures by roughly 15 percent,” the authors wrote.

Further: “These changes in firm behavior persist throughout the chairmanship and begin to reverse after the congressman relinquishes the chairmanship. We also find some evidence that firms scale back their employment, and experience a decline in sales growth.”

In other words, pork doesn’t really juice the local economy. Some Cochran projects demonstrate that.

Barbour and Cochran scored a big victory in 2008 when they brought $580 million in federal money for low-income housing, and then diverted it to an economic development project in the Port of Gulfport, promising 5,000 jobs.

Five years later, the U.S. Department of Housing and Urban Development studied the project and found that the pork project has failed to deliver. "They're still spending money. Money is going out every month and nothing is being done,” Glenn Cobb of the Port's Pathways to the Port Jobs Program said on the local Fox affiliate. “It was told to us that they created something around 1,000 jobs," for port workers, but Cobb "found out it was only roughly 50 jobs.”

The federal money helped build up the port, but the project used up some resources, such as equipment and material, that could have gone to more economically productive activities in the state.

That’s not to say Cochran’s earmarking benefits no one. Look at who’s working overtime to get the Senator reelected: Lott and Barbour, who are both K Street lobbyists. Their colleagues are all in, too. In a pre-primary analysis, I found $100,000 in donations from D.C. lobbyists to Cochran — with over half of that money coming from lobbyists who work on federal spending bills.

Pork and federal largesse enrich the insiders while hurting the businesses in the senator’s home state and providing little or no economic benefit to the home state economy as a whole.

This is the question at the heart of the Mississippi Senate runoff. And this is what’s at stake in the broader Republican civil war: Should Republicans grow or shrink the federal behemoth that enriches the insiders at everyone else's expense?