For President Barack Obama, the American people are sending an unambiguous signal -- create jobs, or else: Obama's approval rating sank to an all-time low of 40 percent, according to a Gallup Poll.

The 40 percent level is considered the danger zone for American presidents by political scientists. A sustained drop below 40 percent would effectively eliminate much if not most of the president's leverage within his own party.

Essentially, members of his party, in this case the Democrats, continually ask, Can I benefit from supporting the president? Or is it better for me, from an electoral standpoint, if I oppose him?

Some members of the other party, at least, historically, ask the same question. However, recently, in today's highly-polarized, partisan Washington political environment, the question pertains primarily to Democrats, given a very cohesive and conservative Republican caucus, particularly in the House.

Approval Rating Down From 50 Percent A Year Ago

Four months ago, Obama's approval rating was at 50 percent; a year ago, it was at 50 percent, in September 2010.

In addition to skirting the 40 percent  danger zone, Obama's approval rating has deteriorated in another key metric: Support among Independent voters.

In late August, only 47 percent of Independents said they approved of the way Obama was handling his job as president, down from 59 percent in late May/early June.

Obama's support level among Independents is critical because the group is the largest unknown in the electorate. Most Democrats will vote for Obama and almost all Republicans, by a much larger percentage, will vote against him. The Independents, a majority of whom supported Obama in the 2008 presidential election, are the swing vote.

In the latest poll, Obama's support among Democrats also fell 11 percentage points, to 75 percent from 85 percent.

Obama's standing among Republicans, already low, sank further, to 11 percent from 16 percent.

Support Also Down Among Lower-Income Americans

Obama also lost support among an income group that's considered to be part of his base: voters earning less than $24,000 per year. Only 45 percent said they approve of Obama's performance, down from 51 percent in May/June.

Other income group support was as follows:

$24,000-59,000: 38 percent, down from 50 percent

$60,000-$89,000: 40 percent, down from 50 percent

$90,000 and up: 38 percent, down from 54 percent

Political Analysis: The approval numbers are grim: Obama's approval rating dropped as the U.S. economic recovery has slowed, and the two aren't unrelated. Also, as noted, Obama's approval rating has dropped to the point where his own party will begin to back away from some of his initiatives.

Equally significant, the 40 percent level means if the presidential election were held today, it would be a close race, and Obama could easily lose in several hypothetical match-ups.

The only bright spot for Obama? The election isn't today -- its 14 months from now, hence Obama has time to gain the support of a majority of Americans. The No. 1 issue in the electorate? Jobs creation. Americans -- across the electorate -- want their president to find ways to create jobs: the unemployed want work, and those employed are concerned about their job security.

Further, the view from here argues that Obama's reelection chances will hinge on his ability to lower the nation's 9.1 percent unemployment rate between now and June 2012 -- the time by which most Americans have decided whom to vote for.