With the House expected to vote Thursday on a measure that would make it easier for workers to unionize, a business coalition launched a six-figure radio ad campaign late Tuesday in an attempt to convince three Democratic freshmen who represent conservative districts to defy organized labor and vote against the bill.

Reps. Nancy Boyda (Kan.), Tim Mahoney (Fla.) and Heath Shuler (N.C.) were all elected in Republican-leaning districts in November, and the business group Coalition for a Democratic Workplace — saying these Members ran as “pro-business” Democrats — is urging their constituents to call them and register displeasure with H.R. 800. The bill would give workers the option of checking a card to indicate their desire to unionize, as opposed to current regulations that mandate secret-ballot elections.

“All three of these Members ran as pro-business Democrats, and we want to make sure that every single freshman Democrat who ran as a new kind of Democrat votes like one,” said Todd Harris, a Republican operative who is serving as a spokesman for the business coalition.

The coalition’s effort joins a U.S. Chamber of Commerce radio campaign already under way in opposition to the labor legislation. At a cost of roughly $500,000, it is targeting 51 Members, including 22 Republicans who represent labor-heavy districts or are seen as possibly inclined to support H.R. 800.

Neither Boyda, Mahoney nor Shuler seem particularly worried that supporting H.R. 800 will cause them re-election problems next year, as all three plan to vote in favor of the bill. In fact, Boyda and Shuler are co-sponsors.

Boyda said the mail she’s received from constituents has been overwhelmingly supportive of her position on H.R. 800. Although Kansas’ 2nd district was represented by Republicans from 1994 to 2006, it was held by Democrats for 24 years before that, and Boyda said her district is more pragmatic than conservative.

“We’re not wealthy people in the 2nd district. It’s a district of working families,” Boyda said Tuesday in a telephone interview. “They may be sorry that they spent their money to tear me down on this one. They may be sorry, but we’ll see.”

The 60-second radio ad targeting the three freshman Democrats is scheduled to run for almost a week on all of the major news-radio stations in their districts, as well as on some highly rated country and mainstream music stations. The linchpin of the coalition’s campaign, as referenced in the ad, is that Democrats have demanded the Mexican government mandate secret ballots for Mexican workers who want to unionize, while they oppose them for American workers.

The bill, dubbed the Employee Free Choice Act, would allow workers the option of checking a publicly viewable card indicating their desire to unionize, eliminating the current method that mandates secret-ballot voting supervised by the federal government.

Supporters say the bill would eliminate corporate coercion against unionizing and make it easier for workers to organize; opponents claim the bill would subject workers to intimidation by union officials, discouraging those who are against unionization from voting that way.

House Republicans leaders, making a concerted push to defeat the bill, met Tuesday with members of the Coalition for a Democratic Workplace to strategize on coordinating opposition to H.R. 800, as well as minimizing the number of Republicans who might vote for the bill.

The six House GOP leaders who met with the coalition included Minority Leader John Boehner (Ohio), Minority Whip Roy Blunt (Mo.) and Chief Deputy Minority Whip Eric Cantor (Va.). Among the coalition’s members are the U.S. Chamber of Commerce, the National Association of Manufacturers and the National Federation of Independent Business.

“Anyone who thinks [Thursday] is going to be the only vote is kidding themselves. The message was, don’t give up the fight, we have our work cut out for us over the next couple of days,” said Danielle Ringwood, a spokeswoman for Associated Builders and Contractors, another coalition member.

Ringwood did not want to speculate on the outcome of Thursday’s scheduled floor vote, but said House Members of both parties tend to oppose the bill — if not at least question its merits — once they’re educated on what it would do. But she said organized labor has drummed up support practicing an effective game of “coercive lobbying.”

The AFL-CIO, which held events in 90 Congressional districts with 150 House Members over the Presidents Day recess, is cautiously optimistic that H.R. 800 will pass the House.

Bill Samuel, the union’s spokesman, said many Democrats from Republican-minded districts are unlikely to face reprisals at the ballot box for supporting the bill, because they represent areas that are culturally conservative but labor-friendly.

That is why freshmen like Boyda and Shuler, who represent districts that tend to vote for Republican presidential candidates, are co-sponsoring the bill and do not fear a political backlash in next year’s elections, Samuel said. The same goes for Mahoney, who is one of just seven or eight Democrats who is not co-sponsoring H.R. 800.

Samuel predicted that as many as two dozen Republicans could ultimately vote for the bill.

“What does it mean to be a red-leaning district where you have a large labor population?” Samuel asked rhetorically. “They may be culturally conservative, but they line up very closely with organized labor.”

The business coalition argues that the option of “card-check” unionization — or “majority sign-up,” as organized labor prefers — will lead to intimidation by union officials, as workers who oppose forming a union will be loath to do so using the publicly viewable card-check or sign-up forms.

Additionally, the coalition claims, 16 Democratic Members have publicly demanded that the Mexican government preserve secret balloting as the only means by which its workers can vote for unionization. Business groups say American workers should not be given any fewer protections than Mexican workers, and they believe this argument will resonate with the public if they can get the message out.

The coalition uses an August 2001 letter that liberal Democratic House Members wrote to Mexican officials encouraging them to “use the secret ballot in all union recognition elections.” The coalition’s radio ad tries to make the point.

“Your vote. In America it’s as sacred as the Constitution. And it’s cast in private,” the ad’s voice-over begins. “But union bosses want to change that. They want you to choose in public. Yes public.”

After some additional rhetoric, the ad concludes: “What’s worse? The same liberal leaders want to protect private ballot elections for workers in Mexico. Private ballots for Mexico and open ballots for Americans. That’s crazy.”

Tory Newmyer contributed to this report.