Rep. Mike Simpson (R-Idaho) easily defeated Bryan Smith in an expensive House primary Tuesday that pitted the business wing of the GOP against the tea party insurgency.

The campaign was the latest staging ground for a fight that is playing out across the country this year. Business groups are redoubling their efforts to protect more moderate Republicans against tea party challengers in races such as the one in Idaho’s 2nd District.

“I think the business community is being much more diligent and thorough in the process of investing time and resources in primaries,” said David French, the chief lobbyist at the National Retail Federation, whose political action committee supported Simpson.

Idaho was one of six states where voters went to the polls Tuesday. Other marquee House primaries included a Pennsylvania contest that former congresswoman Marjorie Margolies (D) lost despite strong support from Bill and Hillary Rodham Clinton. Another former House member, Bob Barr, advanced to a July 22 GOP runoff in Georgia’s 11th District.

Thanks in large part to heavy spending from outside groups, Simpson, 63, a close ally of Speaker John A. Boehner (R-Ohio), had a 26-point lead over Smith, with about a quarter of precincts reporting.

Smith, a lawyer, catapulted into the national spotlight when the Club for Growth backed him last summer. After soliciting responses over the Internet, the anti-tax group bestowed on Smith its first-ever crowdsourced endorsement.

Later, the Senate Conservatives Fund and FreedomWorks, two other national tea party organizations, joined Smith’s cause.

But Simpson was boosted by a barrage of outside spending that the tea party groups could not match. Pro-Simpson forces required to report their spending dumped nearly $2.4 million into the campaign, according to the Sunlight Foundation, a hefty sum for the eastern Idaho district, where advertising is inexpensive. Smith allies spent only about $600,000.

The U.S. Chamber of Commerce, the country’s largest business organization, spent $725,000. In one Chamber ad, Mitt Romney touted Simpson’s conservatives credentials. Romney’s endorsement of Simpson carried substantial weight in the district, where many of his fellow Mormons live.

The Club for Growth, which attacked Simpson over his vote for the 2008 national bank bailout program, spent about $500,000 on the race. But in a sign that Smith was not closing the gap against Simpson, the group stopped spending last month. “We have no regrets, and we think it’s telling that some groups associated with K Street spent millions to defend a Republican” incumbent in a safe GOP district, said Club spokesman Barney Keller.

David Wasserman, a House-race analyst with the nonpartisan Cook Political Report, said: “The lesson in Idaho may be that the tea party telegraphed its strategy. They got behind Smith very early.” In doing so, Wasserman added, “they awakened a sleeping giant in the Chamber of Commerce types and Boehner allies.”

In Pennsylvania’s open 13th District, Margolies, the mother-in-law of Chelsea Clinton, lost to state Rep. Brendan Boyle, who had strong backing from organized labor. Bill and Hillary Clinton both raised money for Margolies. The former president also appeared in an ad for her.

Barr, who was on the front lines of the effort to impeach President Clinton and was the Libertarian Party’s nominee for president in 2008, finished second in the race for the seat of Rep. Phil Gingrey (R-Ga.), a candidate for Senate. With most precincts tallied, Barr will face state Sen. Barry Loudermilk in the runoff.

Elsewhere in Georgia, construction company owner Rick Allen won the Republican race to take on Rep. John Barrow, the only white Democrat from the Deep South in the House.

In Arkansas, Democrats are hopeful about competing in the open 2nd and 4th districts, now Republican-held seats.

In the 2nd District, banker French Hill was the winner of a three-way GOP race and will face former North Little Rock mayor Patrick Henry Hays (D) in the fall.

In the 4th District, where Rep. Tom Cotton (R) is leaving his seat to run for the Senate, state House Majority Leader Bruce Westerman won the GOP nomination and will take on former Federal Emergency Management Agency director James Lee Witt (D).