IRS Commissioner John Koskinen, testifying Wednesday at his impeachment hearing on Capitol Hill, defended his record at the agency and said impeachment would be “improper” – but conceded that some of his past testimony regarding the agency’s targeting of conservative groups “later proved mistaken.”

Koskinen, speaking before the House Judiciary Committee, said he “testified to the best of my knowledge” in prior appearances. But he said: “The truth is that we did not succeed in preserving all of the information requested and some of my testimony later proved mistaken. I regret both of those failings.”

Koskinen, though, urged against impeachment as he faces allegations he obstructed congressional investigations of IRS treatment of Tea Party organizations.

Documents his lawyers released last week noted that he told lawmakers in June 2014 that no emails had been destroyed since congressional investigations began. One year later, Koskinen learned that backup tapes containing numerous emails had been erased by IRS workers in March of 2014.

“These are very serious allegations of misconduct,” House Judiciary Committee Chairman Bob Goodlatte, R-Va., said in his opening statement.

Besides opposition from Democrats, though, the push has divided Republicans, won no backing from GOP leaders and has no chance of garnering the votes Congress would need to oust him.

The hearing Wednesday was scheduled as a result of negotiations inside the Republican ranks.

Many GOP lawmakers want to avoid an impeachment showdown in the shadow of November’s elections. That would force them to choose between opposing impeachment and angering conservative voters who want Koskinen’s head, or backing it and alienating independents who could consider the effort overly partisan and confrontational.

Despite numerous probes by Congress, the Justice Department and the IRS’ independent inspector general, no proof has emerged that the IRS’s treatment of conservative organizations was politically motivated or that any documents were purposely destroyed to hide evidence.

The Constitution provides impeachment for “treason, bribery, or other high crimes and misdemeanors.”

Last week, members of the conservative House Freedom Caucus, which has pushed the impeachment drive, agreed to Wednesday’s hearing after dropping plans to force an immediate House impeachment vote. Caucus members conceded they would have likely lost.

However, one lawmaker in that group, Rep. Tim Huelskamp, R-Kan., has not ruled out forcing an impeachment vote before the November elections.

In May 2013, the IRS conceded that during the 2010 and 2012 elections, it subjected conservative groups seeking tax exemptions to excessively harsh examinations. Many groups with those tax-exemptions play major roles in political campaigns, and they are not required to reveal donors.

Koskinen joined the agency in December 2013, after the improper actions occurred. Conservatives say Koskinen hampered congressional probes by flouting subpoenas, lying to lawmakers and presiding over an agency that destroyed thousands of valuable emails.

A focus of those investigations was Lois Lerner, who had led the IRS office that processes applications for tax exempt status. She refused to answer lawmakers’ questions and later retired.

In June 2014, the IRS told Congress that it lost an unknown number of Lerner’s emails when her hard drive crashed in 2011. Then in June 2015, the IRS inspector general said the agency had accidentally erased 422 backup tapes in March 2014 that could have had up to 24,000 of Lerner’s emails.

Koskinen and Democrats have complained that Republicans have skirted Congress’ normal impeachment procedures, which in recent decades have usually begun with a formal, in-depth committee investigation, not just hearings.

Rep. John Conyers, D-Mich., the panel’s top Democrat, said Wednesday that the impeachment push is “destined to fail” – and warned that if it does hit the floor, it would set a “terrible precedent.”

The House needs a majority vote to impeach an official, in effect formally charging them. The Senate holds a trial and needs a two-thirds majority to remove the official from office.

The Associated Press contributed to this report.