But a close examination of these groups and others reveals an array of election activities that tax experts and former I.R.S. officials said would provide a legitimate basis for flagging them for closer review.

“Money is not the only thing that matters,” said Donald B. Tobin, a former lawyer with the Justice Department’s tax division who is a law professor at Ohio State University. “While some of the I.R.S. questions may have been overbroad, you can look at some of these groups and understand why these questions were being asked.”

The stakes are high for both the I.R.S. and lawmakers in Congress, whose election fortunes next year will hinge in no small part on a flood of political spending by such advocacy groups. They are often favored by strategists and donors not for the tax benefits — they typically do not have significant income subject to tax — but because they do not have to reveal their donors, allowing them to pour hundreds of millions of dollars into elections without disclosing where the money came from.

The I.R.S. is already separately reviewing roughly 300 tax-exempt groups that may have engaged in improper campaign activity in past years, according to agency planning documents. Some election lawyers said they believed a wave of lawsuits against the I.R.S. and intensifying Congressional criticism of its handling of applications were intended in part to derail those audits, giving political nonprofit organizations a freer hand during the 2014 campaign.

After the tax agency was denounced in recent weeks by President Obama, lawmakers and critics for what they described as improper scrutiny of at least 100 groups seeking I.R.S. recognition, The New York Times examined more than a dozen of the organizations, most of them organized as 501(c)(4) “social welfare” groups under the tax code, or in some cases as 501(c)(3) charities. None ran major election advertising campaigns, according to the Campaign Media Analysis Group, the main activity of a small number of big-spending tax-exempt groups that emerged as major players in the 2010 and 2012 elections.