WASHINGTON (AP) — Liberals argue that he caved on the debt ceiling. Unions are upset over his handling of unemployment and labor issues. Hispanics brought the immigration debate directly to his campaign doorstep.

President Barack Obama's summer of discontent has been marked by rumblings within his Democratic political base over his willingness to fight congressional Republicans and his approach to fixing the economy.

Liberals disappointed with Obama for compromising with the GOP during the debt-ceiling showdown now are calling on him to hold firm against Republicans this fall. They want him to push a bold jobs agenda while drawing a strong line on taxes and protecting Medicare and Social Security.

In recent weeks, the gripes have become so loud that the president himself acknowledged them during his Midwest bus tour this week.

"I've got a whole bunch of responsibilities, which means I have to make choices sometimes that are unattractive and I know will be bad for me politically and I know will get supporters of mine disappointed," Obama said in Iowa. He claimed progress on the economy, health care and two wars. And, offering his backers a bit of tough love, he added: "Sometimes you've got to make choices in order to do what's best for the country at that particular moment, and that's what I've tried to do."

The complaints — founded or not — are narrowing the tightrope Obama must walk over the next year to keep his base energized while recapturing the independent voters who helped power his win over John McCain in 2008.

Still, for all the complaining, the ultimate impact on Obama's re-election chances is open to question. The president faces no serious primary opponent, and polls show him faring fairly well within his party. Few liberals are likely to support a Republican for president next year.

But angry liberals could refuse to volunteer to knock on doors or make phone calls, a pivotal grass-roots role for a candidate's base of supporters. Disaffected Democrats could keep their wallets closed, hampering small-dollar fundraising over the Internet. Or they could just stay away from the polls on Election Day.

"They want to love him, but he's given them little evidence and his rhetoric is running out of steam," said Princeton professor Cornel West, who campaigned for Obama in 2008 but has become a fierce critic. "We find ourselves between a rock and a hard place. He's going to need high levels of enthusiasm among his base, and it's going to be hard to do that with speeches and no real serious actions or policies."

The liberal angst has surfaced repeatedly over the past year as Obama has faced the reality of divided government in the aftermath of the 2010 congressional elections in which Republicans won the House.

Liberals howled last December when he struck a deal with the GOP to extend Bush-era tax cuts. That reinforced earlier bad feelings from when he dropped the proposed "public option" for a government plan to compete with private insurance as part of the health care overhaul.

Lately, the left has complained that Obama gave up too much in spending cuts during the debt-ceiling fight and failed to extract higher taxes on the wealthy in return.

Now labor is arguing that a jobs agenda Obama will outline next month is long overdue, and unions are cringing when he talks about trade deals and patent reform. Last week, about a dozen trade unions said they would boycott next year's Democratic National Convention in Charlotte, N.C., over frustration on the economy and because the event will be held in a right-to-work state.

Blacks, who are expected to turn out in huge numbers next year to help re-elect that nation's first black president, also are complaining about high joblessness. "Our people are hurting. The unemployment level is unconscionable," Rep. Maxine Waters, D-Calif., said recently at a Congressional Black Caucus meeting in Detroit.

And on Tuesday, Latino activists delivered 35,000 petitions to Obama's Chicago campaign headquarters to protest the record number of deportations on Obama's watch. They oppose a policy allowing police to submit the fingerprints of criminal suspects to the Department of Homeland Security so they can be cross-checked with deportation orders.

"President Obama is doing a smashing job of discouraging, unmotivating and inducing fear among Latino voters," said Roberto Lovato, co-founder of Presente.org.

On the other hand, in a move welcomed by immigration advocates, the Obama administration said Thursday that many illegal immigrants facing deportation despite having no criminal records will be allowed to stay in the country and apply for work permits.

And Obama has won plaudits from gays and lesbians for ending the ban on gays serving openly in the armed services and for ordering his administration to stop defending the constitutionality of the 1996 Defense of Marriage Act, which denies federal recognition to married gay couples.

Obama campaign spokesman Ben LaBolt dismisses questions about liberal enthusiasm for the president, calling them "nothing more than Washington chatter that is not backed up by the facts on the ground."

And most polls do show Obama faring strongly with Democrats.

The president's overall approval rating has trended slowly downward this summer in Gallup's daily tracking polls, hitting new lows for his presidency — about 39 percent — last week. But on average he has barely lost ground among his strongest supporters, averaging 83 percent approval among liberal Democrats compared with 86 percent earlier this year. Among moderate Democrats, 74 percent approve, down from the high 70s in the winter and spring.

A Fox News poll conducted last week found about eight in 10 Democratic voters said they would probably vote to re-elect the president.

"He will have a base problem until the time when an opponent emerges, and then 90 percent of the problem will disappear," said Democratic pollster Paul Maslin. "People will consider the opponent and then he'll look awfully good."

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Deputy Polling Director Jennifer Agiesta contributed to this report.

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Ken Thomas can be reached at http://twitter.com/AP_Ken_Thomas