Starting as a salesman at a cabinetry company, Lonegan "worked his way up, bought the business, and was successful," Gattenby said.
By contrast, he noted that Booker made much of his money through public speaking, and called him an "absentee mayor flying around the country, peddling his failed policies."
Booker made $1.3 million in speaking fees between 2000 and 2012, according to his returns.
Booker and Lonegan are vying for the Senate seat long held by Frank R. Lautenberg, who died in June. The special election is Oct. 16.
Booker reported total income of $1.7 million during the same three-year time period as Lonegan and $3.9 million overall since 1998.
Lonegan filed joint returns with his wife, Lorraine, a teacher. Booker is single. They claimed one of his two daughters as a dependent until 2012.
His campaign could not say how the family's income broke down between Steve and Lorraine Lonegan.
Lonegan and his wife donated about $1,800 to charity between 2010 and 2012, the returns show. Booker gave about $105,000 during the same time period, according to his returns.
"Mayor Lonegan also has a family to raise," Gattenby said, adding that the candidate paid for his older daughter's wedding last year. Specific charities were not listed on either candidate's tax returns.
Last year, the Lonegans paid $97,722 in taxes on taxable income of $465,508, for an effective tax rate of 20.99 percent.
Lonegan was policy director of the New Jersey chapter of the conservative group Americans for Prosperity in 2010, and then served as state director in 2011 and 2012. The group is backed by the billionaire industrialists David and Charles Koch.
Lonegan reported a total of about $380,000 in capital gains for those three years, most recently through the sale of an office building in Maywood, Bergen County, that he had used for the cabinetry business. He sold the business in 2007, Gattenby said.
Lonegan reported a capital gain of $89,509 in 2010. The source of income was blocked out on the documents provided to reporters, but Gattenby said it stemmed from the sale of a house adjacent to Lonegan's in Bogota. Lonegan is a former mayor of the Bergen County borough.
Lonegan reported $54,000 in ordinary dividends through investments made with Morgan Stanley. The specific investments were not listed. His tax returns also show income from investments made in "various" foreign countries. Gattenby said that money - about $8,600 - came from investments made by Lonegan's broker.
Lonegan's investments have not all been successful.
Last year, for example, he reported losses totaling $52,911 on two rental properties. Expenses at the apartment buildings included repairs, mortgage interest, depreciation, taxes, and legal and other professional fees.
Lonegan's campaign released only three years of tax returns - compared with Booker's 15 - because it said it would not have been feasible for reporters to sift through that many forms in just a few hours.
Booker's spokesman, Kevin Griffis, said the Newark mayor "released 15 years of taxes, covering every year since he first joined Newark's City Council. He has set the bar for transparency in this race."
Like Booker's campaign, the Lonegan campaign did not permit reporters to copy the documents.
Booker also said Friday he would step down from the board of his Internet start-up, Waywire, and donate all of his shares in the company to charity. His role as a founder of the company, while holding the job of mayor, drew criticism.
BY THE NUMBERS
Steve Lonegan's income in 2012. Cory Booker earned $512,728 that year.
Effective tax rate Lonegan paid in 2012. Booker paid a tax rate of 36.9 percent.
Amount in millions Booker earned in speaking fees since 2000.
Amount Lonegan earned
in capital gains from 2010
Contact Andrew Seidman at 856-779-3846, email@example.com or @AndrewSeidman on Twitter.