As Obama and Romney ready for second debate, where do polls stand?

The question now is whether Mitt Romney’s gains are due to a temporary bounce from his strong first debate performance, or whether they reflect a fundamental change in standings with President Obama.

As President Obama and GOP presidential nominee Mitt Romney ready for their second debate Tuesday night on Long Island, it’s clear that the electoral race has shifted, with Mr. Romney probably in the lead by a smidgen. The question now is whether Romney’s gains are due to a bounce from his strong first debate performance, which may recede, or whether they reflect a fundamental change in relative positions.

With polls pouring out every day now, it’s hard to keep track of what’s going on. The best approach may be to tune out individual releases and just look at the trend lines of the averages of major surveys.

Of these, the RealClearPolitics rolling average on Tuesday morning had Romney up by three-tenths of a percentage point, 47.4 to 47.1 percent. TPM PollTracker puts Romney ahead by 1.1 percentage points, 48.4 to 47.3 percent.  The Huffington Post average has Mr. Obama in the lead by 0.9 percentage points, 47.4 to 46.5 percent.

All these averages follow a different mix of polls and use different methodologies. We’ll go with the best of three and say it’s likely that Romney has overtaken Obama since the Denver debate.

If the election were held today, Obama might still have an edge because he’s clinging to leads in some important swing states. That’s why polling analyst Nate Silver’s “Now-cast,” which judges the outcome day by day, says that Obama would win 284 electoral votes (and reelection) to Romney’s 253 if Oct. 15 were Election Day.

But Obama’s battleground edge has shrunk as well. Prior to the first debate, the president was ahead in all states rated as tossups by RealClearPolitics, except North Carolina. Since then, Romney has moved ahead in Colorado, where an average of polls shows him up by 0.6 percentage points, and Florida, where he’s up by 2.5 percentage points, according to RCP. Romney’s lead in North Carolina has grown to 4.7 percentage points.

Tuesday night’s debate might matter most in Virginia and New Hampshire, two battleground states where Obama’s lead is slim and has been shrinking, writes RCP political analyst Erin McPike in an interesting state-by-state breakdown of the race.

“If Romney turns in another solid debate performance and chips away further at the president’s support in those two states, he could add Virginia’s 13 electoral votes and New Hampshire’s four ... bringing him to 261,” Ms. McPike writes.

That would put the Massachusetts ex-governor on the cusp of the 270 electoral votes needed for victory. He could close that gap by winning Nevada, where Obama leads by just 1.6 percentage points, and Wisconsin, where Obama now is up by 2.3 points.

In that scenario, Romney wins without having to take Ohio, a key swing state in which Obama has been solid – perhaps due to the US bailout of auto firms, which have a big presence in the Buckeye State.

None of this map plotting would matter if Romney’s recent gains are solely a reflection of voter judgment that he beat Obama in Denver’s word-joust. Such a bounce could be soft and easily reversed by stronger Obama showings in the two remaining debates. After all, during the GOP primary season, debates often drove polls up or down for particular candidates. Remember when Herman Cain was the front-runner?

But as political analyst Jonathan Bernstein notes on his Plain Blog About Politics, Romney’s gains in the averages of major polls actually began well before the first debate. It’s possible that what we’re seeing is the receding of a longer-term Obama bounce caused by a successful convention and Romney’s “47 percent” comments, plus a smaller pro-Romney debate upsurge.

Got that? In other words, we’re almost back to where we were prior to the conventions, when Obama had a slim national lead in the polls. If Romney’s postdebate bounce recedes, Obama should settle back in with a lead of one to three percentage points, Mr. Bernstein writes.

However, conservatives don’t think Romney’s gains are a “bounce,” a word implying that what goes up comes down. As Jennifer Rubin writes Tuesday on her Right Turn blog at The Washington Post, the GOP thinks Romney has changed minds among independent voters and now needs to close the sale with further strong debate performances.

Romney “is well-positioned to cement the initial impression and keep the swing-state electorate moving in his direction,” writes Ms. Rubin.