Last week, Indiana Sen. Evan Bayh said Democrats are betting that perceptions of the health care reform bill will improve once it is enacted. "That is the bet," Bayh told Charlie Rose, "that some of the misconceptions out there will be proven to be false between now and the election."

That's likely a "bad bet," as University of Michigan political scientist Brendan Nyhan wrote on Wednesday.

First, Americans will not experience the most significant benefits of health reform until at least 2013. And we know that when the prescription drug benefit in Medicare passed, the pronounced skepticism that seniors felt did not begin to dissipate for nearly two years -- when they started receiving its benefits.

Second, as I wrote last month, two of the biggest qualms voters express about the reform proposal involve its cost and the role of government. The Kaiser Family Foundation's February tracking survey found that 80 percent of those who oppose the legislation say a "major reason" is that it "gives government too big a role in the health care system," and 73 percent said the same about the idea that "we can't afford to pay for health care reform right now." It should seem obvious that opponents of health reform will continue to push these arguments throughout the year.

Third, to the extent that opposition results from misperceptions involving "death panels" or the placement of bureaucrats "between you and your doctor," the relevant political science research is not encouraging. Nyhan, along with Georgia State University's Jason Reifler, conducted a series of experiments in 2005 and 2006 in which student test subjects read mock news articles featuring misleading statements about well-known but ideologically contentious subjects such as the presence of weapons of mass destruction in Iraq prior to the U.S. invasion. Half of their subjects read articles including only the misleading statements; half read articles that also included a correction.

By comparing the two groups of respondents, Nyhan and Reifler determined that the ideology of the subjects tended to predict reactions. Efforts to correct misperceptions were more likely to succeed among those ideologically sympathetic to the correction, such as liberals to the notion that WMD were never found in Iraq after Saddam Hussein was deposed. But the corrections tended to "boomerang" among those ideologically predisposed to believe the erroneous information. Thus, conservative subjects who had read the correction were even more likely to believe that WMD had been found in Iraq.

The fact that a Republican candidate can, in the same sentence, condemn "government-run health care" and promise to resist efforts to "weaken Medicare" tells us that the "motivated reasoning" that Nyhan and Reifler cited is alive and well in the health care debate. The potential for reducing "misperceptions" among political conservatives in 2010 is virtually nil.

But that said, Bayh may still have a point about the potential for improvement in support for health reform after it is enacted.

First, his argument had "another part," the notion that "it's better [for Democrats] to look strong and effective than it is to look weak and ineffectual." Democrats who change their votes from "yes" to "no" will have a much tougher time arguing that health care opponents are spreading misleading arguments about the legislation, especially if the reform bill goes down to defeat.

Second, while most surveys continue to show more opposition than support when they ask general, favor-or-oppose questions about health reform, the overall popularity of the legislation has been relatively stable since November and may have increased slightly during February.

Third, since these results vary widely depending on question wording, it may be worth looking more closely at two measures asked of the same respondents in the NBC News/Wall Street Journal poll just before the State of the Union address that help explain the variation. The first question asked, "from what you have heard," whether "Barack Obama's health care plan... is a good idea or a bad idea" and also offered the option to "just say so" for those who "do not have an opinion either way." Forty-six percent said "bad idea," 31 percent said "good idea" and 23 percent said they were unsure or without an opinion.

The poll then followed up with a second question: "If the current health care legislation becomes law, will you consider it to be a step forward or a step backward?" Asked this way, the margin closed: 44 percent said it was a step forward and 49 percent said it was a step backward, leaving just 7 percent unable to answer.

So there is a big gap between the 31 percent who are comfortable saying health reform is a "good idea" and the 44 percent who say it would be a step in the right direction. Now consider the following chart (based on data kindly provided by the NBC/Wall Street Journal pollsters), which shows that virtually all of that gap comes from Democrats and independents.

Passage of health reform, particularly if more liberal members of Congress close ranks in support of the bill, may help bump support up slightly. There is certainly much room for growth among Democrats.

Nyhan has his doubts. Although he agreed in an e-mail that Democrats "have a better shot at changing the minds of moderate Democrats and independents than they do with conservatives," he sees no reason to "expect a significant shift in aggregate beliefs about the content of the plan before November. The flow of information is unlikely to shift in a favorable direction and people won't have personal experience with reform until much later."

(Full disclosure: Brendan Nyhan frequently cross-posts at my blog Pollster.com, and Jason Reifler is a former employee from my days as a political consultant.)