While the political world is fascinated by the growing conservative might that is shaking the Republican establishment, a poll released Monday shows that there is unhappiness brewing at the other end of the political spectrum as liberals are becoming more disenchanted with Democrats, whose control of Congress is being threatened in the midterm elections.

The latest USA Today/Gallup poll shows that fewer than one in five of those surveyed approve of the job Congress is doing, statistically the same as the last few months. Approval of Congress has not been above 20% since May and hasn’t passed 30% since a year ago.

Disapproval of Congress has been a steady backbeat to this year’s midterm elections as the GOP has sought to harness voter disenchantment by portraying Democrats as the party of big government and ineffective big spending. Democrats have countered that government spending on stimulus measures has helped create jobs, albeit too slowly, and prevented a bad situation from getting worse.

Ominously for Democrats, the poll shows they are facing a problem from key elements in their base, those who define themselves as liberal or very liberal. A year ago, an absolute majority of the very liberal and close to half of the liberals approved of Congress, but now a majority disapproves.

Part of the disenchantment could be how Democrats have governed. Democrats tout their progressive actions such as health insurance reform, tougher regulation of Wall Street actions and a more than $800-billion stimulus bill that independent congressional analysts say has created millions of jobs.

But from the liberal perspective, the healthcare insurance overhaul was far less than what they wanted as was the Wall Street financial reform bill. Even the stimulus efforts have been criticized as too little to seriously help bring the unemployment rate down fast enough.

The administration has repeatedly defended all of its programmatic efforts, quoting Voltaire’s wry comment that “the perfect should not become the enemy of the good,” a nod to the political difficulties of getting anything through the Congress, given GOP obstinacy and splits in the Democratic ranks.

Though Democrats tend to enjoy an enrollment edge over Republicans, GOP voters tend to be more enthusiastic and more likely to vote, according to most polls. That is especially true this year, when conservative candidates have ridden the popular discontent and anger to capture GOP nominations in half a dozen states. Democrats have yet to offset that “tea party” movement enthusiasm edge, though Obama has stepped up his campaign attacks and other Democrats have stressed the danger of victories by conservative candidates they dismiss as “wackos and fruit loops.”

The drop in approval of Congress closely tracks Obama’s decline during the same period, according to the Gallup poll, indicating a likely frustration by voters with all current political leadership. Still, the vast majority of incumbents who are running are expected to win again.

The poll was based on telephone interviews with a random sample of 1,019 adults between Sept. 13 to 16. It has a margin of error of plus or minus 4 percentage points.

michael.muskal@latimes.com

Twitter.com/LATimesmuskal