DENVER (August 7, 2012)—Some Republicans are worried that GOP challenger Mitt Romney is going too far in savaging President Barack Obama's green jobs initiative.

At issue is a comment by a Romney campaign spokesman that Congress should let a tax break for wind energy producers expire at the end of the year.

One Iowa congressman suggested Romney lacked a "full understanding" of how important the credit is to Iowa and the nation and the Obama campaign circulated fact sheets showing deep support for the credit in swing-voting states including Iowa, Colorado and Nevada.

Mr. Obama will appear Wednesday in Colorado to promote his economic plan, and it's possible that the wind tax credit could come up.