WASHINGTON – Mitt Romney, one of the wealthiest candidates ever to seek the presidency, paid nearly $2 million in federal taxes on $13.7 million in income that he and his wife reported last year, his U.S. returns showed Friday. That came to an effective tax rate of 14.1 percent, lower than millions of middle-income Americans but actually more than he had to pay.

Most of Romney’s income was from investment returns. That is why his rate was lower than taxpayers whose income was mostly from wages, which can be taxed at higher rates.

Romney’s taxes have emerged as a key issue during the 2012 presidential race with President Barack Obama. Romney released his 2010 returns in January, but he continues to decline to disclose returns from previous years – including those while he worked at Bain Capital, the private equity firm he co-founded.