DICKSON, Tenn. (AP) — The most expensive U.S. House race in the country will be decided Thursday in Tennessee’s primary, where voters pick the nominees for three open congressional seats and governor.

The candidates for the 8th District seat being vacated by Democratic Rep. John Tanner have spent $5.2 million on the race so far, according to data compiled by the Center for Responsive Politics. And that figure doesn’t include another $1.3 million spent by one candidate’s brother as an independent expenditure.

Tanner’s seat and another one being vacated by fellow Democratic Rep. Bart Gordon are at risk of turning Republican in November. The third open seat was created by Republican Rep. Zach Wamp’s decision to run for governor.

Wamp is challenging Knoxville Mayor Bill Haslam and state Senate Speaker Ron Ramsey for the GOP nomination to succeed term-limited Gov. Phil Bredesen, a Democrat. Businessman Mike McWherter, son of former Gov. Ned McWherter, is the only Democrat running.

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Among Democratic House races, the most closely watched contest is in the 9th District, featuring the former Memphis mayor trying to become congressman by telling voters to back him because he is black.

In the 8th District, the GOP establishment choice and early favorite was farmer and gospel singer Stephen Fincher, but physicians Ron Kirkland and George Flinn mounted strong challenges through their financial clout.

Flinn, a radiologist and broadcaster who lives just outside the district in Memphis, has poured nearly $3 million of his own money into his bid, while Kirkland has benefited from the heavy support of his brother Robert, the co-founder of a national home decor retailer Kirkland’s Inc.

Robert Kirkland has run polls, direct mail and television ads, including a recent one that claims that for Fincher “becoming a politician is more important than telling the gospel truth.”

Fincher’s rivals have taken out ads to criticize his collecting $3.2 million farm subsidies. Ron Kirkland’s campaign cites U.S. Department of Agriculture statistics showing that 10 percent of the wealthiest farmers receive nearly three-quarters of all farm subsidies.

“Subsidies are subsidies, whether they go to General Motors or whether they go to farmers,” Kirkland said at a recent campaign stop in Dickson.

Fincher has tried to deflect criticism by arguing that he had nothing to do with the way the current system for supporting farmers was set up, and that he supports unspecified reform of the complicated program.

The subsidies talk has resonated with tea party activists, but not all voters are persuaded.

“Kirkland doesn’t know anything about farm subsidies,” said Craig B. Laman, 69, a businessman from Alamo. “I’m voting for Fincher.”

The Republican winner will face longtime Democratic state Sen. Roy Herron, who had $1.2 million on hand at the end of the last reporting period.

In the 6th District, sparring over the growth of immigration and diversity in counties east of Nashville have dominated the GOP primary to replace Gordon. The leading Republicans, state Sens. Diane Black of Gallatin and Jim Tracy of Shelbyville and former Rutherford County Republican Party Chairwoman Lou Ann Zelenik, have spent a combined $1.6 million, and each has launched at least one attack ad.

Zelenik caused a firestorm when she said in June that plans to build a mosque in Murfreesboro threatened the state’s moral and political foundation.

The race in the heavily Republican 3rd District in southeast Tennessee features Robin Smith, the former chairwoman of the state GOP, against largely self-funded Chattanooga attorney Chuck Fleischmann.

Smith, who has been endorsed by the anti-tax Club for Growth and the U.S. Chamber of Commerce, while Fleischmann has earned the support of Mike Huckabee, who won the GOP presidential primary in Tennessee in 2008.

The state party under Smith’s leadership drew national attention during the presidential election for running a press release showing Barack Obama in what it called “Muslim attire” and a YouTube video targeting Michelle Obama that prompted her husband to say in a national television interview that the party should “lay off my wife.”

In the 9th District, former Mayor Willie Herenton has raised almost no money but plenty of controversy by telling voters in the majority black district to vote for him because he’s African-American. Incumbent Democratic Rep. Steve Cohen has argued that the city is beyond racial politics.

Copyright 2010 The Associated Press.