Public employee unions may be taking a shellacking in Wisconsin and Ohio, but that has not discouraged the unions representing federal employees from vying to recruit 44,000 airport screeners. It is the largest unionization effort of federal workers in the nation’s history.

By next Tuesday, the screeners, employees of the Transportation Security Administration, are to finish casting their votes on whether to unionize. Almost everyone agrees that they will choose to do so.

That may seem surprising when so many public employee unions are being forced into wage freezes and paying more toward health coverage and pensions, and when they have become the target of widespread public criticism. Many Republican leaders say public employees should not be allowed to bargain collectively, asserting that it pushes up costs for taxpayers and impedes management’s flexibility. What is more, they warn, letting airport screeners unionize could jeopardize national security if strikes and work slowdowns crippled airports and resulted in inadequate security checks.

“F.B.I., C.I.A. and Secret Service personnel do not have collective bargaining for good reason, and T.S.A. personnel should be no different,” said Senator Roger F. Wicker, a Mississippi Republican who sponsored a bill that would have stripped the screeners of the right to unionize. The Democratic-controlled Senate voted it down last February in a party-line vote.