The Arizona Democrat had been her party’s last remaining holdout on the package, now slated to move forward on Saturday and pass the Senate within days.
The tax agency said its commissioner asked the Treasury Department’s inspector general for tax administration to look into the audits after The Times raised questions about them.
The former F.B.I. director and his deputy, both of whom former President Donald J. Trump wanted prosecuted, were selected for a rare audit program that the tax agency says is random.