Today’s WaPo/ABC national tracking poll shows Mitt Romney leading President Obama, 50 percent to 47 percent (a “statistically insignificant” margin as WaPo makes sure to note at the top of its story). Still, it’s the first time Romney hit the 50-percent mark in this poll, and a sign Romney’s momentum isn’t fading:

As Romney hits 50, the president stands at 47 percent, his lowest tally in Post-ABC polling since before the national party conventions. A three-point edge gives Romney his first apparent advantage in the national popular vote, but it is not one that is statistically significant with a conventional level of 95 percent confidence. 

However, Romney does now boast a statistically — and substantively — important lead on the economy, which has long been the central issue of the race. When it comes to handling the nation’s struggling economy, 52 percent of likely voters say they trust Romney more, while 43 percent say they have more faith in the president. 

More remarkable than Romney’s advantage on economy is his advantage with independents. It’s not even close:

These advantages with independents undergird a sizable, 19 percentage-point Romney lead over Obama on the horse race. Should that advantage stick, it would be the sharpest tilt among independents in a  presidential election since Ronald Reagan’s 1984 landslide win. (Reagan won independent and other unaffiliated voters 63 to 36 percent, according to the exit poll). Obama won them by eight in 2008.

The poll’s party ID breakdown isn’t terrible: D/R/I is 34/30/32. In 2008, the numbers were 40/33/28. Considering the enthusiasm shift since then, you’d expect Republicans and Democrats to be more evenly split this time around, but plus-4 for Dems isn’t nearly as bad as some of the previous WaPo/ABC polls have been.

The pro-Romney tilt among independents explains the Obama campaign’s recent focus on motivating the base with “zingers” instead of pivoting to the center. A 19-point deficit with independents sounds insurmountable, but the overall race is still within the margin of error. Obama will need massive turnout from his base if that’s the case. As the Post reports, that would be the highest advantage since Ronald Reagan won independents by 27 points in his 49-state reelection sweep.