President Obama and Republican presidential nominee Mitt Romney are once again tied nationally with just days to go in the 2012 campaign, according to the latest Washington Post-ABC News tracking poll.

Among likely voters, Obama and Romney are deadlocked at 48 percent. For the first time this year, the two contenders are also tied among political independents, with 46 percent apiece. Before this poll, Romney had been consistently ahead with these potentially critical voters.

While Obama has evened the score with independents, the challenger has made gains of his own. Heading into Nov. 6, 53 percent of likely voters express favorable impressions of the former Massachusetts governor, right in line with the 54 percent who view the president favorably.

The close competitiveness on “favorability,” the most basic test of popularity, amplifies uncertainty about the election’s outcome. When Presidents Ronald Reagan, Bill Clinton and George W. Bush won reelection, they were all more popular than their opponents. When President George H.W. Bush lost in 1992, he was less popular than challenger Clinton was at the time. There is no modern precedent for an incumbent being at parity with the challenger on this front.

The last time that opposing presidential candidates - regardless of incumbency - were so closely paired in favorable ratings was in 2000. Some 46 percent of likely voters rated Bush favorably, and a similar 44 percent rating for Vice President Al Gore. That election famously ended in a near popular vote tie.

Romney’s improved image stems in part from how he performed in the three presidential debates. Fully 62 percent of likely voters say Romney's debate performances are a factor in their votes, and among the 26 percent who call those a “major factor,” Romney leads Obama by nearly 2 to 1, or 63 to 34 percent.

Voters are evenly divided about whether Obama’s handling of the Hurricane Sandy response is or is not a factor in their vote. Obama had received broad, bipartisan praise for how he dealt with the initial aftermath of the storm that ripped through the East Coast last week.

The Post-ABC tracking poll is a series of consecutive, one-night “waves” of interviews reported as a rolling, multi-night average. The new results are for interviews conducted Oct. 30 to Nov. 2, among a random sample of 1,809 likely voters. The results have an error margin of plus or minus three percentage points.