By Niels Lesniewski and Meredith Dake

Senate Republicans fired another warning shot Thursday in their ongoing battle against the Internal Revenue Service’s treatment of conservative organizations. The latest came at the Finance Committee’s markup of the broad “tax extenders” package, when GOP Sen. Pat Roberts floated an amendment to block, for one year, the IRS from making new rules governing political activity by social welfare groups under section 501(c)(4) of the tax code.