Washington (CNN) – Passage of the landmark health care bill appears to have boosted President Barack Obama's approval rating, but it has not affected his re-election chances so far, according to a new national poll.

A CNN/Opinion Research Corporation survey released Monday indicates that 51 percent of Americans approve of the job Obama is doing in the White House, with 48 percent saying they disapprove. That 51 percent approval rating is up five points from a week ago, before Congress approved the health care reform bill and the president signed the legislation into law. Four in ten respondents say they disapprove because Obama is too liberal and 6 percent say they the president is not liberal enough.

Full results (pdf)

Eighty-six percent of Democrats questioned say they approve of the job Obama is doing, a surge of 12 points over the past week. The poll indicates that 47 percent of Independents approve of the president's performance, up 6 points in a week, and 12 percent of Republicans give him the thumbs up, basically unchanged from a week ago.

"Some parts of the Democratic base, particularly lower-income Americans and union households, appear to be coming back into the fold," says CNN Polling Director Keating Holland. "Obama's approval rating changed the most among Americans who make less than $25,000 a year - the group that is most likely to benefit from the new health care law."

Among union households, the president's approval rating soared 9 points to 58 percent.

Health care appears to be behind the jump in Obama's overall rating. While the president's ratings on the economy and foreign affairs remained static over the past week, his numbers on how he's dealing with health care rose five points to 45 percent, although a majority still disapprove of how he's handling the issue.

"But short-term gains for Obama don't necessarily translate into long-term strength," adds Holland. "In a hypothetical 2012 presidential election match-up, Obama and an unnamed Republican are virtually tied, with no significant change between last week's poll and this one."

A CNN survey released earlier Monday indicates that 56 percent of the public disapproves of the new health care legislation, with 42 percent approving. On Tuesday, the president is set to sign into law a companion bill that makes changes to the main legislation he signed last week.

More than three in ten questioned say they dislike most of the bill, with one in four saying they oppose all of the provisions of the new law. Fifteen percent say they approve of the new law without reservation, with another one in four saying they support the new reforms but feel they didn't go far enough.

When it comes to health care, Republicans have made "repeal and replace" their battle cry, and Obama has said he welcomes the fight. At an event in Iowa City, Iowa, last week, the president scoffed at the GOP strategy. "My attitude is - go for it," he said.

According to the poll, 47 percent agree with the Republican strategy and want Congress to repeal most of the major provisions in the law and replace them with new proposals. But 50 percent are fine with the current law or want Congress to go back and pass something that would increase the government's involvement in health care even more.

Forty-seven percent of respondents say that this is a major victory for Obama, and another one in five call it a minor accomplishment and one in three say it was not a positive development.
The CNN/Opinion Research Corporation poll was conducted Thursday through Sunday, with 1,009 adult Americans questioned by telephone. The survey's overall sampling error is plus or minus three percentage points.

–CNN Deputy Political Director Paul Steinhauser contributed to this report.