WASHINGTON – President Barack Obama is preparing to face down the GOP in what may be one of the defining issues of his presidency: addressing the long-term deficit. House Republicans have united behind a plan to slash trillions in federal spending in part by privatizing Medicare and slashing Medicaid.

Amidst uncertainty about how Obama will handle the challenge, liberals are nervous that he may entertain cuts to the safety net programs that have come to define Democratic politics.

Though Obama has made some moves that have pleased liberals -- such as repealing "don't ask, don't tell" and calling for more infrastructure investments -- here are five policy decisions the president has taken since the 2010 midterm elections that have annoyed the base that propelled him to the White House.

1) Cutting $39 Billion In Domestic Spending

Last week's fiscal 2011 funding measure that Obama hailed as an "historic" success contained the highest level of year-to-year budget cuts in U.S. history, prompting liberal fears that the president was enshrining the GOP view that reducing spending will reinvigorate the economy. It cut into a multitude of programs related to education, health care, environmental protection and scientific research, among others, and disproportionately harmed low-income Americans. Despite all that, defense spending got a $5 billion boost.

2) Giving Up On Civilian Trials For Terror Suspects

Unable to persuade Congress to close Guantanamo Bay or transfer prisoners to the United States for civilian trials, the Obama administration threw in the towel and lifted the freeze on new military trials at the offshore detention center. Liberals charged that denying 9/11 plotter and Khalid Sheikh Mohammed and other suspects a civilian trial codifies the view that the U.S. is not committed to upholding the rule of law in the ongoing battle against terrorism.

3) Intervening In Libya Without Asking Congress

Liberals are split on whether Obama's multilateral air-based military campaign in Libya aimed at preventing a humanitarian catastrophe was a good idea. Skeptics gripe about the cost, the open-ended parameters of the mission, and the need to focus on the home front. But the president's decision to send in U.S. forces without seeking the approval of Congress so aggravated some that Dennis Kucinich slammed it as "an impeachable offense."

4) Extending The High-End Bush Tax Cuts

After Republicans threatened to block the continuation of tax cuts for the middle class if Democrats rescind the special exemptions for the rich, Obama gave in and accepted a package that extended all the Bush-era tax cuts for two years, which he hailed as a compromise. In the process, he undermined a campaign promise to raise marginal taxes on the highest-income earners, a core aspect of the progressive vision of government. Obama has said he plans on pushing for an end to those top-bracket tax cuts as a 2012 campaign issue.

5) Appointing Corporate Executives To Key White House Positions

Heading into the second half of his first term, Obama selected as his new chief of staff William Daley, a former JPMorgan executive who was previously Commerce Secretary in the Clinton administration. Soon after, he appointed General Electric CEO Jeffrey Immelt to helm his new council on job creation. Amidst persistently high unemployment following a financial meltdown fueled by Wall Street recklessness, his decision to have corporate executives make key White House decisions didn't please liberals.