By Erin McPike - April 6, 2012

This week's de facto opening of the general election battle brings a new mathematical reality into focus, and it's only slightly less complicated than GOP delegate math.

After two presidential elections that engendered familiarity with Ohio's all-important 20 electoral votes, and the whopping 27 that Florida carried, there's a new electoral map -- and computation -- with which to contend. So, get used to hearing about the Buckeye State's two-fewer 18 electors and the Sunshine State's two-greater 29. And be prepared to hear more about Pennsylvania’s critical 20 and Arizona’s wild 11, all of which could throw calculations off course.

What hasn’t changed: The magic number to win is still 270.

When potential electoral values are assigned to the two opposing camps, both sides look to John Kerry’s wins on the 2004 map as a base line for President Obama -- and John McCain’s victories in 2008 as a starting point for Mitt Romney. In the minds of the political class, these focal points will always indicate an uphill climb for the challenger.

That is because assuming Obama wins the 19 states (and the District of Columbia) that Kerry did, he will net 246 electoral votes. (That’s five fewer than the 251 those states yielded in 2004, thanks to reallocation following the 2010 census.) McCain notched just 173 electoral votes in 2008. Fast-forward to this year, and the states McCain won translate to 180, which Republican officials assume will all be in the bag for Romney.

Should President Obama carry those 246 electors, winning Florida’s 29 electoral votes alone would get him to 275 and clinch a second term -- though the Obama campaign insists that there are dozens of other ways they can also win. Those various pathways rely on states where the president’s team has been building massive organizations and where Obama leads Romney in the polls. Still, winning the 246 “assigned” to him is a big assumption, because it takes as a given that he will carry Michigan, Wisconsin and Pennsylvania -- three economically depressed Rust Belt states Republicans hope to put into play. Nevertheless, even without one of those, the president’s still-larger starting point underscores the daunting task Romney faces as he begins to execute his swing-state battle with the incumbent.

A Quinnipiac poll released on March 28 showed Obama leading Romney by just 45 percent to 42 percent in Pennsylvania, traditionally a Democratic stronghold. But the president scored larger margins over Romney in the more traditional swing states of Ohio and Florida in surveys by the same pollster.

One benefit to Romney, however, of the prolonged primary process is that as he winds down his battle with Rick Santorum (and softens his negative attacks, which have not reflected well on him), he’ll spend several weeks hitting Pennsylvania’s media markets ahead of the April 24 primary. “We have an excellent opportunity over the next several weeks to introduce Mitt Romney to Pennsylvania voters,” said his spokesman, Ryan Williams. “It’s a state that Governor Romney intends to win in the general election.”

Obama campaign officials dispute the notion that the Keystone State is slipping based on one poll. And yet, they don’t consider it won either. The campaign opened its 14th office in the state on Wednesday and is planning to play hard there. The president visits often, as does native Vice President Joe Biden -- in part because staging a major speech just a few hours’ drive from Washington is a cinch compared to many other swing states across the country. Most important, they note, is that Democrats enjoy a huge voter registration advantage -- 1 million -- over Republicans there.

Taking Pennsylvania off the table would lower the president’s starting number to 226 and make his options tougher, but the campaign stresses that they are playing in so many states because they refuse to get caught in a situation in which they must win a single state or else lose the White House. So late last year, Obama campaign manager Jim Messina laid out six pathways to victory -- though he said about 40 potential combinations exist.

In one map Messina discussed, “the expansion path,” the president could lose Pennsylvania (and New Hampshire) so long as he wins a new state like Arizona in addition to Nevada, New Mexico, Colorado, Iowa and Virginia. Such a combination might be a tall order, though, but it rules out the need to win other, perhaps tougher, states like Ohio, Florida and North Carolina. And yet, that specific combination would allow the president to sneak by with just 272 electoral votes.

Republicans feel confident about challenging the president in the majority of those states, but they acknowledge that Romney’s pathways to victory are narrower than the president’s.