For the first time in his presidency, President Barack Obama’s job approval rating dipped below 40 percent in the latest Gallup tracking numbers.

While the number — 39 percent — has been seized on by Republicans as evidence of Obama’s vulnerability, it’s the longer term trend in the Gallup data that should be more concerning for Democrats. (Gallup’s daily tracking poll is a rolling three-day average, making any one data point the simplest of snapshots in time.)

President Obama’s job approval number hasn’t been higher than 44 percent in more than a month in Gallup polling and with a few occasional bumps has been trending steadily downward since the start of the summer.

The reason for Obama’s slippage in national polling, which has been paralleled by problems in swing states like Pennsylvania and Florida, is no secret: Americans continue to grapple with a stuttering economy and feel as though Washington is providing no real solutions.

(Not for nothing: Congress is at record low approval rates as well in all sorts of polls, a reflection, wethinks, of just how alienated people feel from Washington and its inhabitants.)

The fight over raising the debt ceiling appears to have been a critical moment for many Americans as they saw a nation’s capital at war with itself and few tangible solutions for average Americans being discussed by politicians.

The sense of discontent that the debt debate created was quickly followed by the downgrading of the U.S.’s credit ratings by Standard & Poor’s — a move that sent the stock market into wild gyrations that continued through the end of last week.

All of that consternation and anxiety lands, fairly or unfairly, at the President’s feet. (We’ve written before that presidents, as a general rule, get too much credit for a strong economy and too much blame for a weak one.)

With Congress out of session and the idea of a second major economic stimulus a political impossibility, President Obama is taking the show on the road, literally, with a bus tour through Iowa, Illinois and Minnesota aimed at assuaging voters’ concerns about the direction the economy is headed.

The tour is a recognition by the White House that Obama has to appear to be an active presence when it comes to improving the economy even if the reality is that he can’t do much in the near-term to drastically lower the unemployment rate or create major numbers of new jobs. (It's also an acknowledgment of the centrality of the rural Midwest to Obama’s re-election chances in 2012.)

History provides some reason for hope for President Obama. While his current job approval is lower than any of the last three presidents to win a second term at this point, two of the three saw considerable increases in their numbers before election day.

At this point in 1983, Ronald Reagan’s job approval stood at 43 percent but by October 1984 had soared to 58 percent. Ditto Bill Clinton who in August 1995 had a 46 percent job approval score but by October 1996 carried a far healthier 54 percent rating.

The exception to that rule was George W. Bush whose approval rating was at 59 percent in August 2003 but dipped to 47 percent by October 2004. Bush’s number may well be anomalous because in August 2003 he was still benefiting from positive feelings directed toward him after the Sept. 11, 2001 terrorist attacks.

(Sidebar: Do yourself a favor and bookmark Gallup’s presidential job approval center. It’s a GREAT resource.)

What strengthened the political hands of Reagan and Clinton were economies in recovery, however. It’s not clear whether Obama can hope for the same — particularly with even optimistic economists predicting the jobless rate will remain over 8.5 percent through the 2012 election.

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