As Hillary Clinton's favorability drops week after week in the polls it's down to 43 percent the real question is: Will she start losing the support of those who are the core of President Obama's electoral strength?
In every poll of Obama's favorability or job rating, his positive numbers have never fallen below 39 percent. This is because his coalition of African-Americans, Hispanics, students, single mothers, gays and union people stand by him.
Regardless of events, reversals or failing conditions, the president never loses their support. His favorability is measured on a scale, not 1 to 100 but rather 40 to 100. Those first 40 points are like a golf handicap for our president.
George W. Bush, by contrast, had no such safety net as president. When the Iraq War and then the economy fell apart, his approval rating fell to 27 percent near the end of his second term.
So, as Clinton's ratings drop, will she fall through the 40 percent safety net Obama has used to bolster his numbers? Phrased differently, will the Obama coalition stand by Clinton or abandon her as times turn tough?
This is, of course, the question on which the whole 2016 presidential election hinges.
The Obama base seems to be suspending judgment. Gallup polling shows a 7 percentage-point drop in Clinton's favorability rating since early May. She dropped from 50 percent to 43 percent in that timespan. But her unfavorable rating remained flat at 46 percent. No increase there. So the Americans in those 7 points moved from being Clinton fans to being undecided about her.
The initial indications are that Clinton cannot count on the loyalty of the Obama base and that the 40 percent threshold will not be a firewall for her candidacy.
While her overall favorability is not yet low enough to test the firewall, her ratings for being honest or trustworthy indicate that she can, indeed, drop below 40 percent without being rescued by the Obama base.
When Quinnipiac pollsters asked whether Clinton is "honest and trustworthy," only 33 percent of Iowa voters said she was. In Colorado 34 percent saw her as honest and trustworthy and in Virginia 39 percent. So, at least as far as integrity is concerned, the firewall is not holding.
Those who today say she is neither honest nor trustworthy but are undecided about their overall opinion of her are likely to come down on the negative side within a few months.
As the debates near, the impact of Clinton's diminishing popularity among Democrats will become clearer. When liberals see Sen. Bernie Sanders (I-Vt.) live and in the flesh, embracing their programmatic fantasies a $15 minimum wage, a lower retirement age, a 90 percent top tax bracket, a single-payer healthcare system there will be no residual affection for Clinton to hold them back.
Democrats are likely to go through a process: First they won't trust Clinton, then they won't like her, then they will be undecided, and finally they will end up backing Sanders or one of her other rivals.
If the Obama firewall won't hold for Clinton, look for her to fall even further behind in head-to-head match-ups with Republican candidates.
Already, tracking polls in Iowa, New Hampshire and Virginia show her trailing the likes of GOP candidates Jeb Bush and Scott Walker. When she starts losing these swing states by double digits and begins to fall behind in national polling, the Democrats will get the clear message that Clinton can't win.
Their discontent will stimulate others to join the race. Vice President Biden will look at entering. Sen. Elizabeth Warren (Mass.) may come in. Or Sanders could begin to beat Clinton in key states.
It is all unraveling for Clinton. So, will the Obama safety net hold? If it doesn't, we will have a Republican president.