With 187 delegates at stake, the outcome could prompt some undecided super delegates to choose sides.
For voters, high food and gas prices have made the economy the #1 election issue.
This morning in North Carolina, Clinton continued her with her populist message. She didn't back down from her summer gas tax holiday proposal; even though a recent New York Times survey shows most voters believe its political pandering. "I want the gas companies to pay for the first time and make them part of the solution," said Clinton.
Obama is trying to show working-class voters he's not out of touch. He opposes the gas tax break. "They don't need a short-term gimmick. The oil companies will just raise the rates," said Obama.
In spite of important wins in the battleground states of Pennsylvania and Ohio, Clinton is behind in the popular vote and overall delegate count. But Obama's lead in the national polls has softened with the Reverend Wright and the "bitter and guns" controversies.
For Obama, solid wins in both states could pressure Clinton to get out. But Clinton victories could prolong this already drawn-out race until June and beyond.