The Post’s polling guru Jon Cohen noted the latest evidence that President Obama is losing Jewish support:

Fully four in 10 Jews now disapprove of the way President Obama is doing his job — up significantly from late spring — according to the latest numbers from the Gallup tracking poll.

Overall, Obama continues to score considerably higher among Jews than he does overall — he is at 55 percent approval and 40 percent among those surveyed by Gallup from the beginning of August through Sept. 14 — but the negative trend also matches that among other groups. . . .

In May, 68 percent of Jews said they approved of Obama’s performance in office, that slipped to 60 percent in June and is now under that level for the first time this year. Disapproval has gone from 26 percent in May to 32 percent in June to the new 40 percent level.

I asked Cohen’s colleague Peyton Craighill if Gallup was more reliable than some earlier surveys. He told me that the Gallup methodology is solid. “They aggregate their daily tracking poll (1,000 interviews a night) so they get enough of a sample through random polling procedures.”

It’s important to note that these voters are registering discontent, but they are a long way from casting votes for a GOP challenger. That suggests that the Obama campaign will have to spend time and money trying to keep these votes in the fold, rather than spend effort on constituencies that have historically been less loyal to the Democratic Party.

What we do know is there is a critical mass of disenchanted Jewish voters. Can one of the Republicans pick up some of this support in the form of donors, volunteers and, ultimately, voters?

This is one example of why it is critical for GOP contenders to be able to reach out to voters who haven’t been traditionally (or at least recently) voting Republican. In a similar vein, my colleague Greg Sargent notes that about a third of independent voters are turned off and less likely to vote for Texas Gov. Rick Perry because of his position on Social Security. Conversely, Perry might be able to gain ground with Hispanic voters (who are also abandoning Obama in droves) by maintaining his moderate position on immigration and support for in-state tuition breaks for those who may be or whose parents may be illegal immigrants.

The challenge for the Republican contenders is to be true to their conservative values while making themselves appealing to voters outside the base. Sometimes that means articulating a position more strongly (e.g. support for Israel), sometimes that means resisting the urge to freak voters out (especially those who don’t think Social Security is a “failure”) and sometimes that means being brave enough to take heat from the base (reject nonsense on HPV vaccination’s “dangers”). It’s not easy. But then running for president is a tough endeavor.