Under current rules, social welfare organizations may conduct some political work as long as it's not their main activity. The proposed new rules would block such things as running ads that "expressly advocate for a clearly identified political candidate or candidates of a political party" as fulfilling their tax-exempt mission. Ads that simply mention a politician to, for instance, urge him or her to vote a certain way couldn't be run 60 days before a general election or 30 days before a primary.
The rules also would limit voter drives and voter registration efforts and distribution of literature.
Congress passed a stand-alone measure to block the IRS from issuing the rules for a year. The Democratic-controlled Senate has ignored it.
Tuesday's legislation also would cut the IRS' budget by $1.5 billion below President Barack Obama's request, sending it to Bush administration levels.