BOSTON – If the release of several years of tax returns by Republican U.S. Sen. Scott Brown and his likely Democratic challenger, Elizabeth Warren, proved anything, it was simply that they are both well-off Americans who have earned millions in recent years and are in some of the highest federal tax brackets.

The returns were made public on Friday after days of bickering by the campaigns over when and how the release should occur.

In the end, Brown made six years of returns available for inspection by journalists at his campaign headquarters but didn’t post them online or allow copies to be removed. Warren posted four years of abridged returns on her website and allowed journalists to review the returns in their entirety at her headquarters.

While Brown is not remotely as wealthy as the state’s other U.S. senator, Democrat John Kerry, or the late Sen. Edward Kennedy, Democrats said Brown’s returns undercut both the “regular guy” image he has cultivated and his campaign’s repeated attempts to paint Warren, a Harvard Law School professor, as an out-of-touch liberal elitist.

Brown and his wife, television reporter Gail Huff, together reported earning more than $2.5 million in the six years from 2006-2011. Their income rose dramatically after his upset victory in the January 2010 special election to fill Kennedy’s seat.

The increase was largely due to the $1 million Brown received from a publisher for his memoir “Against All Odds” — $700,000 in 2010 and $300,000 in 2011, though he also reported more than $100,000 in expenses related to the writing and subsequent promotion of the book.

In 2011, the couple’s income was reported at $510,856, and he paid $123,642 in taxes at an effective rate of 24.2 percent. Brown and his wife earned $243,781 in wages in 2011, including $142,821 from the U.S. Senate, $85,130 from Huff’s salary from her employer, Allbritton Communications, and $15,780 that Brown earned from his service in the Massachusetts National Guard.

In 2010, Brown and his wife reported income of $839,520 and paid $237,447 in taxes at an effective tax rate of about 28.3 percent.Warren and her husband, Bruce Mann, also a Harvard law professor, reported income totaling nearly $3.4 million over tax years 2008-2011 and paid more than $944,000 in federal taxes during that period.

Their top earning year was 2009, when Warren earned $347,933 and Mann $341,041 from Harvard. Warren also earned $147,468 for consulting and lecturing and was paid $128,433 as chairwoman of a congressional oversight panel for the Wall Street financial bailout. The couple paid $282,210 in federal taxes that year at an effective rate of 28.8 percent.

In 2011, Warren and Mann reported total income of $616,181 and paid taxes of about $159,200. Warren’s salary from Harvard dropped to $82,673 that year as she launched her campaign for Senate.