The National Association of Manufacturers is ramping up its lobbying effort against pro-labor legislation as Congress heads back to work.

NAM is launching a direct mail and advertising campaign through its Labor Policy Institute opposing the Employee Free Choice Act.

The initial phase of the campaign will be directed at Arkansas and Colorado, according to a NAM press release.

“This bill is one of the greatest threats to manufacturers’ economic competitiveness,— NAM Executive Vice President Jay Timmons said in a statement. “We want to remind manufacturers and the public that this bill would destroy jobs. The EFCA would send our economy and our nation in the wrong direction.—

Colorado Democrat Michael Bennet and Arkansas Democrats Mark Pryor and Blanche Lincoln are seen as key votes on “card check.—

NAM declined to disclose the amount it is spending on the campaign. NAM spokeswoman Maureen Davenport said NAM is going to focus on earned media and grass-roots activities.