WASHINGTON - A slice of corporate America thinks tea partyers have overstayed their welcome in Washington and should be shown the door in next year's congressional elections.

In what could be a sign of challenges to come across the country, two U.S. House races in Michigan mark a turnabout from several years of widely heralded contests in which right-flank candidates have tried - sometimes successfully - to unseat Republican incumbents they perceive as not being conservative enough.

In the Michigan races, longtime Republican businessmen are taking on two House incumbents - hardline conservative Reps. Justin Amash and Kerry Bentivolio - in GOP primaries. The 16-day partial government shutdown and the threatened national default are bringing to a head a lot of pent-up frustration over GOP insurgents roughing up the business community's agenda.

Democrats hope to use this rift within the GOP to their advantage. Rep. Steve Israel, D-N.Y., chairman of the House committee to elect Democrats, insists there's been "buyer's remorse with House Republicans who have been willing to put the economy at risk," and that it is opening the political map for Democrats in 2014.

That's what the Democrats would be expected to say. But there's also Defending Main Street, a new GOP-leaning group that's halfway to its goal of raising $8 million. It plans to spend that money on center-right Republicans who face a triumvirate of deep-pocketed conservative groups - Heritage Action, Club for Growth and Freedom Works - and their preferred, typically tea party candidates.

In one race, the group plans to help Idaho eight-term Rep. Mike Simpson, who faces a Club for Growth-backed challenger in a GOP primary.

"These conservative groups have had it all their own way," said former Republican Rep. Steve LaTourette of Ohio, head of the new group. "They basically come in with millions of dollars and big-foot a Republican primary and you wind up with these Manchurian candidates who are not interested in governing."

LaTourette said that for the past three years, some "40, 42 House members have effectively denied the Republican Party the power of the majority" that it won in the 2010 election by blocking the GOP agenda.

Defending Main Street is meeting Nov. 5 in New York with wealthy potential donors.

Call it the wrath of establishment Republicans and corporate America, always considered the best of friends. Since the Republican takeover of the House in 2010, they've watched the GOP insurgents slow a transportation bill and reauthorization of the Export-Import Bank, block a treaty governing the high seas and stand in the way of comprehensive immigration legislation.

The final straw was the bitter budget standoff that partly shuttered the government, precipitated by Republicans like Amash and Bentivolio who enlisted early in the campaign demanding that President Barack Obama dismantle his health care law in exchange for keeping the government operating.

Even after 16 days of a shutdown, falling poll numbers for the GOP and a threatened economy-jarring default, the two broke with their House Republican leaders and voted against the final deal to reopen the government.

Long before the shutdown, the U.S. Chamber of Commerce, which has spent tens of millions boosting mainly Republicans in congressional races, urged the GOP to fund the government and prevent a default, then double back and try and work out changes to the health care law later.

A significant number of House Republicans have given a cold-shoulder to the Chamber's agenda. Rob Engstrom, the group's political director, said the Chamber will see how races develop before deciding on its involvement next year.

The latest political dynamic promises to affect the midterm elections - but how? Republicans hope the widespread animosity generated by the shutdown dissipates by next November and they can hold their House majority. Currently, Republicans control 231 seats and Democrats 200. Democrats are widely expected to win the special House election in Massachusetts for the seat of Sen. Ed Markey and would need to gain 17 seats next year to seize control.

"As long as we stay focused on the priorities of the American people, I think we're going to be fine," House Speaker John Boehner, R-Ohio, said last week when asked about whether the GOP can hold onto the House.

What about the Michigan races?

In the state's 11th Congressional District, just northwest of Detroit, David Trott, a businessman involved in real estate finance and a member of the Michigan Chamber of Commerce Board of Trustees, is challenging Bentivolio.

In the 3rd Congressional District in the southwest part of the state, Brian Ellis is a 53-year-old Grand Rapids businessman who owns an investment advisory firm and serves on the school board. He describes himself as the true conservative Republican in the race, criticizing Amash's votes against Rep. Paul Ryan's budget that cut nearly $5 trillion and a measure reducing taxes for small businesses.

Ellis makes it clear that he would have sided with Boehner on the House GOP's last-ditch plan to avoid default. He says it never would have reached that point if Republicans hadn't embraced the tactic of linking the health care law to government funding.

"I certainly agree that Obamacare is an 'Obama-onation,'" Ellis said in an interview. "But I think the tactic, especially threatening to default on our debt, that is very reckless and not a good way to run our country. I'm in the financial world and I know that would have some far-reaching consequences that would not be good."

In seizing on the rift, Israel and Rep. Jim Himes of Connecticut, the Democratic Congressional Campaign Committee's national finance chairman, sent a letter to more than 1,000 business leaders reminding them that Democrats voted unanimously to end the shutdown and avoid default while House Republicans "turned their backs on business in favor of the radical demands of the tea party."

Republicans dismiss this Democratic outreach to the business community as wishful thinking.

"I don't think Democrats will be successful because the biggest headwinds we face in the economy right now are of their making, from regulation to the Affordable Care Act to this obsession with higher taxes," said Rep. Kevin Brady, R-Texas. "Certainly the uncertainty of the last month has not been helpful, but that's on top of a heap of other uncertainty."

Even if the business community isn't ready to embrace Democrats, Israel insists that the recent budget stalemate has helped his candidate recruitment while boosting the campaign committee's fundraising. At the end of September, the committee had $21.6 million on hand to $15.7 million for the National Republican Campaign Committee.

Potential recruits who Israel jokingly said had put his number on the "do-not-call-list" have suddenly been announcing their candidacies, including Democrat Pete Festersen, the president of the Omaha City Council, who is running against eight-term Rep. Lee Terry, and attorney Bill Hughes Jr., who is looking to unseat 10-term Rep. Frank LoBiondo, R-N.J.