COULD Hillary have a lock on the Keystone State?

The latest Daily News/Franklin & Marshall poll shows U.S. Sen. Hillary Clinton expanding her lead to 16 points over U.S. Sen. Barack Obama in the Democratic presidential primary in Pennsylvania.

The survey of registered Democrats found Clinton leading Obama 51 to 35 percent among likely voters, with an even larger lead of 50 to 28 percent among all voters.

"Hillary Clinton has been running a very tough, flat-out race in this state, aggressively courting voters, and I think it's paying off," said poll director G. Terry Madonna.

"She's been in every region of the state, speaking to large and enthusiastic crowds, and Obama has really not put on a full-court press here," Madonna said.

Obama has visited Pennsylvania about half as often as Clinton since the March 4 Texas and Ohio primaries.

Clinton's strength in the latest poll reversed gains Obama made in the February survey, which showed him pulling to within 12 points as his campaign surged nationally.

The good news for Obama may be that the survey caught Obama at a low point, but before his widely praised speech on Tuesday.

The poll was conducted from March 11-16, when stories were surfacing about controversial remarks from Obama's former pastor, the Rev. Jeremiah Wright.

Madonna said the Wright controversy helps account for a noticeable jump in Obama's negatives with 25 percent of those polled saying they had an unfavorable view of him, up from 16 percent a month ago.

The state's demographics favor Clinton with its concentrations of blue-collar Democrats and older white voters, Madonna said, and it's important for Obama to try and close the gap before the April 22 primary.

"He needs to compete here, because the popular vote count matters, because he doesn't want her making the argument that she wins the big swing states, and because he needs to establish that he can win among blue collar voters, one of the core elements of the Democratic party," Madonna said.

The poll showed Clinton winning among voters in union households by a whopping 67- to 26-percent margin. And while Clinton beat Obama in all income groups, she performed best among households with incomes of $35,000 a year or less, where she won 65 percent to 25 percent.

The poll also showed clear trends in racial and gender preferences.

Clinton led among women, 57 percent to 29 percent, and white voters by an identical 57 percent to 29 percent. Obama led among non-white voters 76 percent to 12 percent and split the male vote with Clinton just about evenly.

Clinton showed broad ideological appeal, winning among self-identified liberals, moderates and conservatives.

Roughly one in five of each candidate's supporters said they would vote for Republican John McCain if their candidate didn't win the Democratic nomination.

Even though the election is still more than four weeks away and neither side has been running television commercials, voters seem to be gravitating toward hard choices.

Undecideds have shrunk to 13 percent among likely voters, and 80 percent of those who expressed a preference said they're "absolutely certain" of their decisions. In the survey a month ago, 37 percent said they could still change their minds.

"We've seen a lot more definition to the race over the past month," Madonna said. "Because there's such a visible national campaign, voters are settling into a choice."

Clinton remains strongly associated with health care in voters minds, Obama more with the war in Iraq.

The economy remains the leading concern for Pennsylvanians, with 39 percent saying it's the most important issue, as opposed to 23 percent citing the Iraq war, and 18 percent citing health care.

By a margin of 59 percent to 19 percent, voters found Clinton "more qualified" to be president. They also said Clinton "would make the most positive changes," but by a smaller margin over Obama, 47 percent to 33 percent.

Asked which candidate would make progress on a variety of issues, voters said Clinton was more likely to improve the economy than Obama by a margin of 54 percent to 25 percent.

But voters rated the candidates more closely on other issues, such as ending the war in Iraq (Clinton 40 percent, Obama 34) and improving America's world image (Clinton 45 percent, Obama 39).

Asked who would best reduce the income gap between rich and poor Americans, voters picked Obama, 34 to 33 percent. *