I’ve obtained some previously unreleased data from this week’s Washington Post poll that probes in some detail whether Obama is at risk of losing support on his left — a claim that has been widely made by pundits in the wake of his compromises with the GOP on tax cuts and spending cuts.

The upshot: Some of the numbers suggest potential cause for worry, though others suggest that the left may be sticking with him in the numbers he needs, despite some signs of softening support. Here are some of the key findings, sent my way by the Post’s polling team:

* Among liberal Democrats, Obama’s strong favorability rating has dropped 10 points, from 79 percent in April to 69 percent now.

* Among liberal Dems, the percentage of those who view Obama as ”too conservative” has jumped seven points, from eight percent last September to 15 percent now.

* The percentage of liberal Dems who say they will “definitely” not vote for Obama has gone up eight points, from one percent in December, to nine percent now. (The flipside here is that the percentage who will definitely vote for him has gone up seven points, to 72 percent.)

* The percentage of liberal Dems who say Obama is “doing too much to compromise” with the GOP on “important issues” has gone up five points, from 20 percent in December to 25 percent in March (though that’s within the margin of error).

However, these numbers are balanced by other findings that suggest Obama is holding steady on his left:

* Obama’s “strong job approval” among liberal Democrats has generally held steady; it’s now at 61 percent.

* Obama’s “strong” approval on the deficit has gone up eight points, from 44 percent in March to 52 percent today; and it’s increased six points on the economy in the same period, to 58 percent.

Those numbers echo other polls that show Obama’s approval holding steady with liberals.

The question is whether general approval numbers are adequate in assessing whether Obama has to worry about his standing among liberals. More important than such numbers may be ones measuring the enthusiasm of the Dem base — which might indicate whether they’ll come out to vote in 2012 or volunteer or donate money to his campaign. By this standard, the numbers above showing slippage — the strong favorability rating; the view of Obama as too compromising — could conceivably be cause for a bit of concern.

In fairness to Obama, he has embarked on a new and agressive strategy in recent days — regularly making an expansive moral case for liberal governance and sharply contrasting it with the GOP’s vision — which could end up diminishing the warning signs over time. That is, if he stick with this approach and doesn’t give away too much in the battles to come.

UPDATE: These numbers show differing time frames because they reflect the fact that previous Post polling has asked different questions at different times.