The Obamas earned $4.2 million last year

By: Mark Memmott and Jill Lawrence

Tax returns just released by Democrat Barack Obama's presidential campaign and posted online here show that he and his wife Michelle had an adjusted gross income in 2007 of $4.2 million. Most of that was thanks to his two books. Obama earned slightly more than $3.9 million in royalties from Dreams From My Father and The Audacity of Hope.

The senator and his wife paid nearly $1.4 million in federal taxes last year and gave $240,370 to charities -- or about 5.7% of their income.

On March 25, Obama released the tax returns he and his wife filed for the years 2000-2006. Those showed that their income soared after he became a national figure in 2004 with his speech at the Democratic National Convention and election to the Senate. Sales of his books skyrocketed, pushing the couple's income from $208,000 in 2004 to $1.7 million the next year.

On April 4, Bill and Hillary Rodham Clinton released details from the tax years 2000-2007 that showed they earned about $20.4 million last year and $109 million over those eight years.

Hillary Clinton's presidential campaign has challenged Obama to release even more of his tax records -- those covering the years in the late 1990s when he was a state senator in Illinois. The Clintons' tax records have been public for about 30 years, since Bill Clinton became governor in Arkansas.