Notably, several other Washington, D.C.-area newspapers, including the Washington Post and the Washington Times, circulate their papers in Virginia's northern suburbs, intensifying the competition.
In the fierce battle for Florida's 29 electoral college votes, today's endorsements of Obama and Romney by the Tampa Bay Times and the Orlando Sentinel, respectively, are major boosts.
Still, several other endorsements remain: The Tampa Tribune, which endorsed McCain in 2008, has also not revealed its endorsement, and the pick of the Miami Herald, which endorsed Obama in 2008, is also not known.
New Hampshire is a tiny state with a potentially big electoral impact. Similarly, the Manchester Union-Leader has typically played an outsize role in electoral politics. It has twice passed up the chance to endorse Romney, who was governor of its next door neighbor, Massachusetts, in 2008 and in 2012. But Romney may still need the state's four electoral votes if he is to secure the presidency in 2012.
Colorado may be one of the most purple states in this year's election, and the endorsements reflect the state's fluid political identity. Obama snagged the biggest prize today with the Denver Post's endorsement. The paper notably endorsed George Bush in 2004. Two other smaller papers, the Colorado Pueblo Chieftain and the Colorado Longmont Times-Call, have endorsed Romney.
Normally, a state squarely in the Republican column, North Carolina shifted to Obama in 2008, giving him a razor thin .3 percentage point win. It's up for grabs again in 2012, with 15 electoral votes at stake.
Last week, one of the state's smaller papers, the Winston-Salem journal, flipped from its position in 2008 to endorse Obama. But two other of the states larger papers have yet to endorse, including the Raleigh News & Observer, which went with Obama in 2008, and the state's largest paper, the Charlotte Observer, which also endorsed Obama.
Nevada cast its lot with Obama in 2008, but with the housing crash hitting the state's economy hard, it is solidly in the undecided column for 2012. The state's largest newspaper, the Las Vegas Review-Journal, endorsed Romney this month. The editorial board endorsed McCain in 2008.
The Las Vegas Sun, another major paper, has yet to endorse in 2012, but it put its name down for Obama in 2008.
The visit Romney made to the Des Moines Register editorial board revealed how seriously his campaign takes its endorsement.
After backing McCain and Hillary Clinton in the primaries, the Register endorsed Obama in the general election. Obama won the state by a wide margin.
The Register has not yet delivered its verdict for 2012, but Romney did win its endorsement in the GOP primary.
Mitt Romney's selection of Rep. Paul Ryan of Wisconsin as his running mate put the normally blue state into play in November. The state's dramatic political shift in the 2010 election toward the Republican Party has added to its swing state status. Its largest paper, the Milwaukee Journal-Sentinel, endorsed Obama in 2008 and Sen. John Kerry in 2004 but has not yet endorsed a candidate in 2012.