I've been following this story pretty closely for months, but I know it hasn't gotten a lot of attention in major media.
So, this video exchange is a pretty good primer on the issue.
For reference: Lois Lerner was in charge of the IRS division that approves and denies tax exempt status for non-profits. The allegation is that she and her allies blocked Tea Party groups from attaining the tax-exempt status for political reasons. This, in turn, limited the ability of Tea Party groups to raise money.
This video is of Rep. Trey Gowdy (R-SC) eviscerating the IRS Commissioner, after it was learned that Lois Lerner's e-mails have been destroyed or lost -- but only during the time frame when she was allegedly targeting the conservative groups.
This is called "spoliation" -- and Rep. Gowdy clarifies what the Congressional investigation is now about.
This should not be a partisan matter. I suspect Democrats would not like a Republican administration using the IRS as a weapon against them, either.
Indeed, it was one of the articles of impeachment filed against President Nixon.