With conservative and liberal activists critical of the Internal Revenue Service regulations for nonprofit groups, the spotlight is shifting to new IRS commissioner John Koskinen, who is under pressure not to finalize regulations that would circumscribe the political activity of groups such as Tea Party organizations.

The proposed rules received 143,615 comments, an IRS record, during a three-month comment period that closed Thursday night.

White House press secretary Jay Carney defended the proposed rules. "This action was recommended by the independent inspector general who had already looked into some of the matters that caused all the concern that we saw last year," he told reporters during the Friday briefing.

The authority to approve the rules lies with Koskinen. “I think the chances of it getting finalized before the November election are fairly slim,” Koskinen told a House Appropriations subcommittee on financial services and general government on Wednesday.

Senate Minority Leader Mitch McConnell, R-Ky., has tried to influence Koskinen, who has the job because then-acting IRS commissioner Steve Miller resigned in response to news that the agency had targeted Tea Party groups -- as he considers finalizing the controversial rules by comparing him to the commissioner who defied Richard Nixon.

“He can either fulfill that mandate to the American people by restoring integrity to an agency they no longer trust. He can be a hero and say no to those who are pressuring him to crack down on the First Amendment rights of ordinary Americans – just like the IRS commissioner who stood up to Nixon," McConnell said Thursday morning.

Koskinen hasn't responded to such appeals. "While we haven’t heard from Commissioner Koskinen yet, we hope and expect to soon," McConnell aide Brian McGuire told the Washington Examiner.

On Thursday, the House passed the "Stop Targeting of Political Beliefs by the IRS Act," offered by House Ways and Means Committee Chairman Dave Camp, R-Mich., which would delay the implementation of new rules for a year.

Even some liberal groups oppose the new rules, which Tea Party organizations fear will be used to target them.

“The proposed rule threatens to discourage or sterilize an enormous amount of political discourse in America,” the ACLU wrote in a comment to the IRS, according to the Washington Post.

Nonetheless, President Obama opposes the bill in the Senate. "In spite of POTUS veto threat, today I will motion that the Senate immediately pass my bill to stop IRS targeting, protect free speech," Sen. Jeff Flake, R-Ariz., tweeted Thursday.