U.S. President Barack Obama and Republican presidential nominee Mitt Romney derided each other Saturday on their campaign trails.

President Obama speaking in Iowa – a state the helped launch his successful 2008 White House campaign – criticized Mr. Romney for rehashing outdated ideas from the 20th century in his address at the recent Republican national convention in Tampa, Florida.

Mr. Romney told supporters at a rally in Ohio, if a “coach” is “zero and 23 million,” it is time for a new coach. The figure was a reference to the number of Americans who are unemployed.

Both candidates are crisscrossing the country as they try to secure votes in a presidential contest that polls say remains close.

The Democratic national convention takes place this week in Charlotte, North Carolina.