DAYTON, Ohio – The endgame at hand, President Barack Obama and Republican Mitt Romney plunged into the final two weeks of an excruciatingly close race for the White House on Tuesday with TV advertising nearing an astronomical $1 billion and millions of Americans casting early ballots in all regions of the country.

Increasingly, Ohio looms as ground zero in a campaign waged in tough economic times. The state’s unemployment of 7 percent is well below the national average of 7.8 percent, Obama has campaigned here more than in any other state, and Romney has booked a heavy schedule of appearances in hopes of a breakthrough.

The economy was the theme Tuesday as the two rivals put their final, foreign policy-focused debate behind them.