A round-up of this morning's must-read stories.

THE FIRST 21ST CENTURY CAMPAIGN
(Ronald Brownstein, National Journal)
In scope and sweep, tactics and scale, the marathon struggle between Barack Obama and Hillary Rodham Clinton has triggered such a vast evolutionary leap in the way candidates pursue the presidency that it is likely to be remembered as the first true 21st-century campaign. On virtually every front, the two candidates’ efforts dwarf those of all previous primary contenders—not to mention presumptive GOP nominee John McCain. It’s easy to miss the magnitude of the change amid the ferocity of the Democratic competition. But largely because of their success at organizing supporters through the Internet, Clinton and, especially, Obama are reaching new heights in raising money, recruiting volunteers, hiring staff, buying television ads, contacting voters, and generating turnout. They are producing changes in degree from prior primary campaigns so large that they amount to changes in kind.

THE KEYSTONE PRIMARY STAKES
(Michael Barone, Wall Street Journal)
Mrs. Clinton will claim that her primary victory (if it turns out to be that) in the nation's sixth largest state shows that she is the choice of the people – especially the white working class which has been the bedrock constituency of the Democratic Party since the 1930s. But the white working class is steadily declining as a Democratic constituency. The demographic composition of the Pennsylvania electorate, which makes it more typical of the America of the 1950s than the America of today, means that its precedential value is limited to its 21 electoral votes (down from its peak of 38 in 1912-1928). Pennsylvanians have kept quiet during most of our history. But they will make some noise when they vote tomorrow – and may make more difference than they have since the days of James Buchanan and Benjamin Franklin.

MORE: For Women Voters in Pa., a Shifting Landscape (Philadelphia Inquirer)
In Pennsylvania, White Male Vote is Key (Christian Science Monitor)

PENNSYLVANIA PRIMARY DECISIVE? SIGNS SUGGEST NO
(Rick Pearson and Mike Dorning, Chicago Tribune)
As the race grows more negative, most signs indicate that Pennsylvania voters won't be the ones to end the historically long primary season. Given polls showing Hillary Clinton with a small but not decisive lead in Pennsylvania, chances are that the contest will be alive and well for voters in Indiana and North Carolina. Both Clinton and Barack Obama are looking beyond Tuesday's primary to voters they might woo between now and early May. Even though Clinton trails Obama in the delegate and popular vote counts thus far, her camp says she will continue trying to convince party leaders that she is more likely to deliver swing states like this one for Democrats in the fall. Polls show Obama has sliced into her once-strong lead here, making her argument more difficult. 

PARTY CHIEFS PLAN PUSH TO AVOID A LONG FIGHT
(Jackie Calmes, Wall Street Journal)
The rising vitriol is prompting more Democrats to demand that party leaders do something to end the battle. But no single leader or clique exists within the fractious party to end the fight, and those with influence insist voters must have their say. Nevertheless, some party leaders are quietly planning to try to end the clash, said people familiar with the matter. After the primaries end in June, these influential Democrats -- led by House Speaker Nancy Pelosi -- plan to push the last uncommitted party leaders to endorse a candidate, in hopes of preventing a fight at the August presidential convention, party insiders say. 

DEM VOTER SURGE COULD CUT CLINTON MARGIN
(Jeanne Cummings, Politico)
According to the Secretary of State’s office, since January about 217,000 new voters have registered for the April 22 primary, the vast majority of whom signed up as Democrats... That statewide Democratic surge has been accompanied by a flood of party-switching. More than 178,000 voters have changed their party status since January — and the Democrats have captured 92 percent of those voters... Those party-switchers now represent about 7 percent of the roughly 2 million Democratic voters expected to turnout Tuesday, said Madonna. A poll of those switchers and new registrants released by Madonna last week found that Obama was the preferred candidate for 62 percent of them. Clinton insiders said they are also bracing for the same 60-40 split among newly registered Democrats. Depending on turnout, Madonna said, those newcomers could help Obama cut a Clinton victory margin by 2 to 3 percentage points and keep her below a double-digit win that would breath new life into the hard-fought race. 

MCCAIN: A QUESTION OF TEMPERAMENT
(Michael Leahy, Washington Post)
Since the beginning of McCain's public life, the many witnesses to his temper have had strikingly different reactions to it. Some depict McCain, now the presumptive Republican nominee for president, as an erratic hothead incapable of staying cool in the face of what he views as either disloyalty to him or irrational opposition to his ideas. Others praise a firebrand who is resolute against the forces of greed and gutlessness. "Does he get angry? Yes," said Sen. Joseph I. Lieberman, a Connecticut independent who supports McCain's presidential bid. "But it's never been enough to blur his judgment. . . . If anything, his passion and occasional bursts of anger have made him more effective." Former senator Bob Smith, a New Hampshire Republican, expresses worries about McCain: "His temper would place this country at risk in international affairs, and the world perhaps in danger. In my mind, it should disqualify him."

OBAMA'S SECRET WEAPON: THE MEDIA
(John F. Harris and Jim VandeHei, Politico)
My, oh my, but weren’t those fellows from ABC News rude to Barack Obama at this week’s presidential debate. Nothing but petty, process-oriented questions, asked in a prosecutorial tone, about the Democratic front-runner’s personal associations and his electability. Where was the substance? Where was the balance? Where indeed. Hillary Rodham Clinton and her aides have been complaining for months about imbalance in news coverage. For the most part, the reaction to her from the political-media commentariat has been: Stop whining. That’s still a good response now that it is Obama partisans — some of whom are showing up in distressingly inappropriate places — who are doing the whining. The shower of indignation on Charlie Gibson and George Stephanopoulos over the last few days is the clearest evidence yet that the Clintonites are fundamentally correct in their complaint that she has been flying throughout this campaign into a headwind of media favoritism for Obama.

OBAMA'S TOUCH OF CLASS
(Thomas Frank, Wall Street Journal)
In truth, I have no way of knowing whether some passage of mine inspired Mr. Obama's tactless assertion that the hard-done-by clutch guns and irrationally oppose free-trade deals. In point of fact, I oppose many of those trade deals myself. But I know one thing with absolute certainty. The media flurry kicked up by Mr. Obama's gaffe powerfully confirms an argument I actually did make: That as they return again to the culture war, what the soldiers on all sides are doing is talking about class without actually addressing the economic basis of the subject.