The latest Gallup poll, conducted April 1-2, puts another nail in the coffin of Bush’s Social Security privatization effort.
Gallup asked about Bush’s plan in two different ways. Here’s the good idea/bad idea version:

As you may know, one idea to address concerns with the Social Security system would allow people who retire in future decades to invest some of their Social Security taxes in the stock market and bonds, but would reduce the guaranteed benefits they get when they retire. Do you think this is a good idea or a bad idea?

The public’s verdict: 61 percent bad idea/33 percent good idea, which is even more negative than the last time this question was asked on March 18-20 when it was 59 bad/33 good.
And here’s the favor proposal/oppose proposal version:

As you may know, a proposal has been made that would allow workers to invest part of their Social Security taxes in the stock market or in bonds, while the rest of those taxes would remain in the Social Security system. Do you favor or oppose this proposal?

This also receives a very negative response: 56 percent opposed/39 percent in favor. Note that this is quite a bit more negative than the previous time (March 18-20) Gallup asked this question when the verdict was close to split (45 favor/47 oppose).
The shift on the second version of the question and the convergence in negativity between the two versions of the question suggest that the public is becoming less sensitive to question wording when asked about Bush’s proposal. They’ve made up their minds what they think about his proposal (they flat-out don’t like it) and any reasonable question wording is going to elicit that strongly negative verdict.
So where does that leave us? Let me turn things over to Max Baucus, Democratic Sentaor from Montana, who Bush once fantasized might be a Democratic vote for privatization:

Frankly, my personal view [is], privatization is dead. It’s not going to be enacted. It’s not going to be enacted because it is so flawed and it is so wrong, and the American people sense that, they feel it, they know it.

You go, Max!
The rest of the Gallup poll is full of yet more bad news for Bush, reflecting the way things have generally been going for him lately. His overall approval rating is 48 percent, with 48 percent disapproval, his second worst approval rating since the election (after last Gallup poll’s 45 percent). His approval rating on the economy is now 41 percent approval/55 percent disapproval, down substantially from 48/49 in late February. His ratings on Iraq (43/54) and terrorism (57/40) are also down from their late February measurements, though less than the economic rating.
Speaking of Iraq, this poll finds a 53-45 majority saying it was not worth going to war in Iraq. Even more significant, for the first time a majority (50-48) says the Bush administration deliberately misled the public about whether Iraq had WMD.
Bringing up the rear on Bush’s approval ratings are, unsurprisingly, Bush’s ratings on Social Security (now 35/57) and on handling the Terri Schiavo case (34/53).
And speaking of the Schiavo case, it now seems clear some serious damage has been to the GOP’s image by the intrusive and ideological way they handled it. As a USA Today story on the new Gallup poll points out:

By 55%-40%, respondents say Republicans, traditionally the party of limited government, are “trying to use the federal government to interfere with the private lives of most Americans” on moral values.
By 53%-40%, they say Democrats, who sharply expanded government since the Depression, aren’t trying to interfere on moral issues….
By more than 2-to-1, 39%-18%, Americans say the “religious right” has too much influence in the Bush administration. That’s a change from when the question was asked in CBS News/New York Times polls taken from 2001 to 2003. Then, approximately equal numbers said conservative Christians had too much and too little influence.

Final note: all this bad news, including the veritable death-knell for Bush’s privatization plan, comes courtesy of a Gallup sample that, as Steve Soto points out, is +4 Republican on party ID, a distribution inconsistent with almost all other recent polls, which have been showing a Democratic edge. So perhaps these results, bad as they are for Bush, may actually be understating his difficulties a bit.