WASHINGTON – A Republican group promoting pro-business candidates as it battles the Tea Party in primary campaigns is being financed mostly by labor unions, one of the Democratic Party's staunchest allies.

Defending Main Street, a super-PAC aligned with the Washington-based Republican Main Street Partnership, received more than 90 percent of its $845,000 in donations last year from labor groups, according to reports filed with the Federal Election Commission.

The group is led by former Ohio Rep. Steve LaTourette, a Republican who had good relations with labor in Congress. He voted for a minimum-wage increase, the 2009 auto bailout and a bill making it easier to organize a union.

That record and LaTour­ette's new alliance with labor though the super-PAC is drawing scoffs from leaders of the small-government Tea Party movement.

"It's not surprising that a liberal Republican who supported big labor's agenda in Congress would raise money from his allies in big labor," Barney Keller, a spokesman for the Washington-based Club for Growth, said in a telephone interview. "It ain't exactly dogs and cats living together. It's more like birds of a feather."

In an odd pairing, given its funding source, Main Street is working alongside the U.S. Chamber of Commerce, the nation's largest business lobby, to defend Republican candidates deemed more practical and economic-minded than the Tea Party recruits.

The union financing for Main Street shows that some labor leaders are hedging their partisan bets, recognizing that Republicans are likely to hold a majority in the House after the midterm elections, and bipartisan allies could be beneficial later.

Sarah Chamberlain, the chief operating officer of the Republican Main Street Partnership, said it's a "win-win" situation for her organization because the labor money will help defend Republican seats. "Why not take union money to maintain a majority in the U.S. House?" she said.