Romney has more than $1 million tied up in each of several Goldman Sachs funds, including as much as $1 million in the Goldman Sachs Small Cap Value A (GSSMX)fund, which seeks long-term capital appreciation in small-cap stocks.

Romney's portfolio also includes an investment of between $1 million and $5 million in the Goldman Sachs Strategic Income A (GSZAX)fund. His wife's trust has between $500,000 and $1 million in the Goldman Sachs Local Emerging Markets Debt Fund A (GAMDX).

Most of Romney's income is from his investments -- although he did make nearly $114,000 serving on the board of Marriott International (MAR, news). He resigned as a director in January 2011. He also made $374,000 in speaker's fees in 2010 and 2011 combined.

Romney has also drawn fire for profiting from investments in Fannie Mae and Freddie Mac -- two entities he has criticized along with two former Democratic senators who, Republicans say, favored Fannie and Freddie. "The failures of Fannie Mae, Freddie Mac, Barney Frank, Chris Dodd are just so legion that we have to rethink about how we're going to support a growing housing industry," Romney said last September, according to the Boston Globe.

But Romney reported investments of between $250,000 and $500,000 in a mutual fund called the Federated Government Obligations Fund (GOIXX), which invests in the debt of Fannie Mae and Freddie Mac, along with other entities. This fund was not part of the blind trust, the Globe reported. Instead, Romney likely would have been familiar with it. Romney's campaign said the investment was made by his charitable trust.

Romney also has millions of dollars in various Bain Capital funds. In his disclosure forms, he said that he hasn't been actively involved with Bain since retiring from there in 1999. His Bain investments were part of his retirement agreements with Bain and are passive in nature, he said.

Income tax returns released

The tax data released this week may not make questions about his tax rate go away. He and his wife paid $6.2 million in taxes over those two years, with a rate of 13.9% in 2010 and 15.2% in 2011. That's lower than a lot of Americans earning far less money pay.

Romney had steadfastly refused to release tax returns in the early months of his campaign, drawing criticism for his hesitation. A Washington Post editorial called it a "striking and disturbing departure" from the past practices of presidential candidates.

"Asking candidates to make their tax returns public is undoubtedly an invasion of privacy," the Post editorial scolded. "But it is one that comes with the territory of a presidential campaign."

Romney pays a low tax rate because most of his income comes from investments; tax rates on capital gains are lower than those on other income.

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In the past, Romney's advisers dumped dozens of stocks that would very likely have made him more money, but were thought to be "politically sensitive," Money magazine reported. Those included the now-private casino operator Harrah's and oil companies that do business with Iran.

Cayman Islands investments

Some of Romney's millions have ended up in Bain investment funds in the Cayman Islands, ABC News reported. As much as $8 million is parked in 12 funds in the Caymans, according to ABC, and another investment of between $5 million and $25 million is domiciled in the Caribbean tax haven.

Romney's campaign says the Cayman accounts help attract money from foreign investors. Generally, investment firms like Bain establish Cayman accounts to draw investors to their funds, profiting handsomely in the process. While the Caymans are widely used as a tax haven, his campaign says Romney gets no tax advantage from the Cayman connection and has paid all taxes on income from those funds.

As much as these financial questions may make campaign managers uncomfortable, there is a bright light for Romney here. It might be better for him to get these out of the way now. If Romney wins the Republican nomination, he can try to steer the dialogue away from his financials and toward topics that benefit his campaign against President Barack Obama.

Of course, with Obama expected to focus part of his campaign on the growing gap between rich and poor, and a need to raise taxes on the rich, shifting the focus away from Romney's portfolio may not be easy.