(CNN) -- Sens. Hillary Clinton and Barack Obama are wrapping up their push in Pennsylvania with sharp attacks a day before the state's crucial primary.

Sen. Hillary Clinton greets supporters Sunday at Pennsylvania State University.

Both candidates have been launching waves of robocalls, tough mailers and matching attack ads, spending an estimated hundreds of thousands of dollars a day.

Both Obama and Clinton made campaign stops in key cities on Monday.

Obama has outspent his rival in Pennsylvania, thanks in part to his hefty fundraising.

He raised $41 million in March, compared with Clinton's $20 million, according to the latest campaign finance reports.

In March, Obama spent about $31 million on his presidential campaign, compared with Clinton's $22 million.

Clinton began April in debt, according to financial reports filed over the weekend with the Federal Election Commission. She had about $32 million cash on hand, but only $9 million of that total represents funds that can be spent in the primary races.

Meanwhile, Obama has $51 million cash on hand, with $42.5 million that can be spent in the primaries, according to reports.

At least $23 million of the money Clinton had in the bank was set aside for the general election, compared with $8 million set aside by Obama.

Clinton on 'Larry King' A day before Pennsylvania's primary, Sen. Hillary Clinton sits down with Larry King on CNN's "Larry King Live."

Tonight, 9 ET see full schedule »

The reports also showed Clinton owes more than $10 million, meaning she was in the red even before stepping up TV advertising in Pennsylvania.

"The numbers are what they are," Clinton adviser Howard Wolfson said on a conference call with reporters.

"The money continues to come in strongly. We had a very good month, last month of fundraising. ... We are continuing to have a good month this month."

He also said, "We will of course be honoring the debt in the coming weeks and months."

Tuesday's contest brings an end to a six-week primary hiatus. With 158 delegates at stake, the Pennsylvania primary is the largest remaining Democratic contest. Watch how the candidates are making their final pitches »

Clinton told supporters Sunday in the historic steel-mill town of Bethlehem that last week's bruising debate and the candidates' recent disputes over health care proposals "showed you the choice that you had."

"I am offering leadership you can count on. You know where I stand, you have known what I have done, and you know what I will do," the senator from New York said.

Clinton said Obama has misrepresented her plan for universal health care in a barrage of mailers and television ads.

"We need to try to achieve universal health care, not create political opposition to universal health care," she said. "That is what the Republicans do, not what Democrats do."

Obama, who has campaigned on messages of change and unity, acknowledged Sunday that his campaign has "elbowed back" a few times in response to criticism from Clinton and her supporters.

"When I hear Sen. Clinton's campaign say they're going to throw the 'kitchen sink' strategy at us, and they try to manufacture or exploit fake controversies instead of talking about what is important for the American people ... then I'm thinking, 'Well, you learned the wrong lessons from those Republicans who are going after you in the same way,' " the senator from Illinois said during a town hall-style event in Reading.

Obama has criticized Clinton's plans for a health care mandate, which would require individuals to purchase insurance and requires insurance companies to offer coverage to anyone who applies.

Clinton has said that Obama's plan, which would create a national health insurance program but would not mandate individual coverage, would leave up to 15 million Americans uncovered.

Obama on Sunday said that any of the three leading presidential candidates -- including Republican rival Sen. John McCain -- would be better than President Bush.

"Either Democrat would be better than John McCain," he said in Reading. "And all three of us would be better than George Bush."

In the past, Obama has equated a McCain presidency to a "third Bush term."

Clinton shot back, saying, "We need a nominee who is going to take on John McCain, not cheer him on."

Obama leads Clinton in the overall delegate count, 1,644 to 1,498, while Clinton has a slight edge over Obama in superdelegates, 254 to 230.

Clinton has seen her double-digit lead in Pennsylvania shrink to 7 percentage points, according to the most recent Pennsylvania Democratic "poll of polls," an average of campaign surveys.

About 7 percent of the state's Democratic voters say they are undecided, the surveys found

The poll of polls consists of three surveys: Zogby (April 19-20), Suffolk University (April 19-20) and Quinnipiac (April 18-20). E-mail to a friend

CNN's Jim Acosta, Alex Mooney and Rebecca Sinderbrand contributed to this report.

All About Pennsylvania • Hillary Clinton • Barack Obama