Three nonprofit advocacy groups that were denied tax exemption by the Internal Revenue Service were all units of Emerge America, an organization devoted to cultivating female political leaders for local, state and federal government.

The I.R.S. denied tax exemption to the groups — Emerge Nevada, Emerge Maine and Emerge Massachusetts — because, the agency wrote in denial letters, they were set up specifically to cultivate Democratic candidates. Their Web sites ask for evidence that participants in their training programs are Democrats.

News of the I.R.S. decision, which surfaced in heavily redacted denial letters to the groups that were posted to the agency’s Web site last Thursday, raised concerns among advocacy groups, known as 501(c)(4) organizations after the section of the tax code that governs them, at large.

Crossroads GPS, a conservative advocacy organization with ties to Karl Rove, the Republican strategist, sent an e-mail to supporters on Tuesday, assuring them that it was not one of the three groups denied exemption.