The polls opened before daylight in Ohio, and many voters were eager to cast their vote. In Texas, an estimated 2 million people elected to beat the rush and cast their ballots in early voting.
Tune in tonight for live updates on tonight's primary results. Check your local listings for The 700 Club, or check back with CBNNews.com, beginning at 7 p.m.. EST.
Both Hillary Clinton and Barack Obama hope tonight's results in all four state contests will work to their advantage.
But after a bitter day of back and forth attacks and responses, there's no love lost on the campaign trail between these two.
Vowing to stay in the race and fight the good fight, Clinton continued to trumpet her national security credentials and accused Obama of political doublespeak for a memo between his campaign and Canadian officials.
"It raises questions about Obama coming to Ohio and giving speeches against NAFTA and having his chief economic advisor tell the Canadian government it's just political rhetoric," Clinton said.
Obama shot back pointing out even the Canadian embassy said the conversation was misinterpreted and then called Clinton out on her own game.
"Senator Clinton and her husband championed NAFTA, worked on behalf of NAFTA , called it a victory, called it good for America - until she started running for president," Obama said.
But the heated exchanges weren't limited to the candidates.
Obama angered reporters for ending this press conference before they could ask him about his dealings with former fundraiser Tony Rezko.
Obama and Clinton are neck and neck in Texas according to the latest polls, with Clinton slightly ahead in Ohio. And this is shaping up to be her toughest fight yet.
Although some Democrats have begun pressuring her to drop out, Clinton's campaign says if she wins either of the big states in play, she can break Obama's momentum and create enough breathing room to beat back those calls.
But with Obama's delegate lead, a growing number of Democrats are weary that a long protracted race will weaken their nominee going into the November elections.