She rolled up over 200 thousand more votes than Barack Obama in winning a 55-45% victory in the Keystone State, getting to that important double digit margin.

"The American people don't quit and they deserve a President who doesn't quit either," Clinton said to cheers at her victory party.

The win again gave a boost to Clinton's argument that big states matter in the race for the White House.

Once again, Obama had the chance to knock Clinton out of this race. But like in New Hampshire, like in Texas and Ohio, Clinton refused to die.

"You made your voices heard," she told supporters in Philadelphia, "and because of you, the tide is turning."

Barack Obama was not in Pennsylvania when the votes were being counted, as he had already moved on to Evansville, Indiana. He gets another chance on May 6th to end this race, with a win in the Hoosier State.

The polls there have been close, giving Clinton a minimal lead. My guess is that lead will go up in the aftermath of this Pennsylvania win.

I'm convinced now that if Clinton wins Indiana, then she's in the race all the way to Montana and South Dakota.

Once again, the county by county map of the results raise questions about Barack Obama's candidacy and appeal in a working class state like Pennsylvania.

As I type this well after midnight, Obama is ahead in just seven of the 67 counties in Pennsylvania. His biggest margins came from the city of Philadelphia, but he did not produce in the suburbs as expected.

This is nothing new for Obama. He won only five counties in Ohio. He won only about 10 percent of the counties in Texas. He won only three counties in Missouri outside of St. Louis and Kansas City.

Hillary Clinton will keep making the case that Obama can't win over Reagan Democrats that are key for the Democrats come November.

Her goal now is to repeat her wins in Ohio and Pennsylvania in Indiana, so she can move on to West Virginia and Kentucky, two more states that seem to be likely victories for Clinton.

This race may well go all the way until Montana and South Dakota vote on June 3rd.