With exactly one month to go until the U.S. presidential election, polls show the race between President Barack Obama and Republican Mitt Romney essentially tied.

The Pew Research Center gives Mr. Romney a four percentage point lead while Gallup puts the president in front by three points.

Mr. Romney closed the gap in the polls after last week's first presidential debate which focused on the economy. Analysts say Mr. Romney appeared more comfortable and prepared while the president gave an uncharacteristically lethargic performance.

Both candidates campaigned Tuesday in Ohio and Iowa — two of the so-called swing states that could decide the election.

Speaking at Ohio State University in Columbus, President Obama urged students to register and vote, saying everything Democrats fought for in 2008 is on the line. He said the country has come too far to turn back to failed policies.

Mr. Romney visited a farm in Van Meter, Iowa and defended his tax plan. He told the Des Moines Register newspaper that he would like to simplify the tax code and cut taxes for the middle class. He said the president's plan to raise taxes on wealthier Americans will not create jobs.

Mr. Romney campaigns Wednesday in Ohio while President Obama returns to Washington.