As we’ve often noted here, polls are see-saws or, another comparison, snapshots in time that can change as starkly as a scene a minute later. But the latest POLITICO/George Washington University Battleground Poll has some good news for President Barack Obama, bad news for Republican Presidential nominee Mitt Romney, and a warning flag for those who suggest the race is somehow over already:

President Barack Obama has opened a national lead in a tight race that’s been static for much of the year.

A new POLITICO/George Washington University Battleground Poll of likely voters finds little good news for Mitt Romney but a race that remains competitive.

Obama leads 50 percent to 47 percent, which is within the margin of error. His 50 percent job approval rating puts him at a crucial threshold for an incumbent seeking reelection. It’s an uptick from the spring and summer, but 48 percent still disapprove.

Romney, meanwhile, finds himself sliding in the wake of two events — the choice of his running mate and the Republican national convention — that were supposed to buoy his candidacy. His unfavorable rating ticked up from 46 percent to 49 percent over the past seven weeks, as the share viewing him favorably held steady at 46 percent.

It’s also instructive to point out how when these two events took place Fox News, conservative talkers and some conservative websites touted them as big successes. There were some who even suggested Clint Eastwood’s talking to an empty chair was a political master stroke.

Personal likability boosts the president, who is viewed favorably by 53 percent.

“The window is narrowing for Romney, and he’s in deep, deep trouble,” Democratic pollster Celinda Lake, who helped conduct the bipartisan poll, said Sunday.

“Ultimately, people don’t like this guy. If they don’t like someone, it’s hard to get people to vote for him — particularly to fire someone they do like.”

The universe of voters who might change their mind also has shrunk significantly. One in five supporting a candidate said they’d consider someone else last month. Now it’s closer to one in 10. Regardless of who they’re supporting, 60 percent now expect Obama to win. Democrats say this will fuel late Obama momentum. Republicans think pro-Obama turnout could drop off if people expect him to win.

The poll’s Republican pollster, Ed Goeas of the Tarrance Group, notes that Romney is winning independents by 2 points.

“Our original premise that this was going to be a very close race is just reinforced with most of this data,” he said. “This race is far from over.”

In fact, the battle will now likely be over that small percentage of voters who are swing voters and undecideds — you know, those voters partisans constantly diss as dumb, or uniformed, or mushy until they really really REALLY need their votes. And if the swing voters and undecideds go their way, then those voters are wise, well wise, well informed, and defending principles.

The bottom line: this race is fluid. She has not sung yet — and any suggestion that she definitely has is a lot of this.

Here’s the Pollster composite of polls today:

And some context from First Read:

*** Polling update: Here’s a wrap of all the recent polling we’ve seen: As mentioned above, the University of Cincinnati poll shows Obama up by five points among likely voters in Ohio, 51%-46%… In Florida, a Tampa Bay Times/Miami Herald/Bay News 9/Mason-Dixon survey has Obama at 48% and Romney at 47%… And there’s a national Politico/GWU Battleground poll of likely voters that has Obama at 50% and Romney at 47%.