Last month’s Supreme Court ruling weakening the Voting Rights Act has left voting-rights advocates and Democrats fearing that a potential new wave of suppression tactics could keep poor and minority voters from the polls. Voter ID laws have topped the list of concerns, with several southern states vowing to push forward with such measures now that it’ll be harder for the federal government to stop them.

But a close look at the research on how voter ID laws affect elections suggests that, from a purely political point of view, the anxiety may be misplaced: The picture is murky, but there’s no clear evidence that requiring voter ID significantly reduces turnout. And some experts say that other voting restrictions—especially those that make it harder to register and to vote early—are likely to have a bigger effect.

“The jury is still out on voter ID,” Daniel Tokaji, a law professor at Ohio State University and a leading expert on voting rights, told msnbc. “But its impact on turnout may not be as great as some opponents fear and some proponents probably hope.”

In other words, if Republicans, confronted with a shrinking base and an increasingly non-white electorate, are pinning their hopes on voter ID as an electoral game-changer, they may wind up disappointed.

Within hours of the high court’s ruling, Texas had announced that it considered its strict voter ID law—blocked last year by a federal court under Section 5 of the Voting Rights Act—to be in effect. (In fact, the state told msnbc weeks before the decision that it would take that view should Section 5 be invalidated.) In North Carolina, the lead sponsor of a Republican-backed ID law said he’d move ahead with the effort in light of the court’s action. Similar laws in Alabama, Mississippi, and Virginia, which had been in limbo thanks to Section 5, now look set to go into effect before next year’s midterms. And that’s in addition to the states pushing strict voter ID that were never covered under Section 5, including Pennsylvania, Wisconsin, and Tennessee.

An Uneven Burden

Experts on voting say the evidence is overwhelming that such laws do more harm than good, by stopping more legitimate than illegitimate voters from casting a ballot. Numerous studies—some based on data compiled by the states themselves—have found both that a significant portion of eligible voters lack ID (many also lack the documents needed to get it) and that blacks and Hispanics are more likely than whites not to have it.

“It really would have a very significant burden on people with less education, people who are minorities,” Matt Barreto, a political science professor at the University of Washington, whose research has been used in numerous legal battles over voter ID, told msnbc.

That suggests voter ID laws are unwise and unfair. But it doesn’t definitively answer the more political question of what impact they have on turnout. After all, what if, for instance, the vast majority of those without ID wouldn’t vote anyway? Again, even if that were the case, it wouldn’t be an argument for voter ID laws, since even people who don’t usually vote have a right to do so. But it’s an important question for voting-rights advocates and—especially—Democrats as they draw up a post-Section-5 triage strategy for protecting access to the ballot.

Since strict voter ID laws began to go into effect over the last decade, there have been numerous attempts by political scientists to measure their impact (see below for brief synopses of some of them). But not only have different studies produced contrasting results, some of the experts who have looked most carefully at the question say it’s difficult to draw any firm conclusions based on the data currently available.

In 2006, the federal Election Assistance Commission (EAC) set out to probe the issue. The study it commissioned, conducted by scholars at Rutgers, looked only at the 2004 election, and considered whether turnout correlated to the strictness of a state’s voter ID requirements. It found not only that a correlation existed, but that the impact on minorities was greater than on whites.

A Murky Picture

But the study was challenged the following year by scholars at the conservative Heritage Foundation, who pointed out that the authors had incorrectly classified the voting requirements of two states, and noted what they said were other methodological problems. After addressing these issues, the Heritage study showed essentially no correlation between turnout and the strictness of a state’s ID requirement.

Perhaps the most careful look at the question, and one that several voting experts held up as the most authoritative, was conducted in 2009 by Robert Erikson and Lorraine Minnite, political science professors at Columbia University and Barnard College, respectively. Erikson and Minnite scrutinized the methodology used in the EAC and Heritage studies, as well as a third study put out in 2007 by scholars at Caltech and Washington Univ. in St. Louis, and conducted their own separate analysis.

“It should be evident that our sympathies lie with the plaintiffs in the voter ID cases,” Erikson and Minnite frankly acknowledged. But although, like the EAC study, they found some relationship between the strictness of voter ID requirements and a decline in turnout, the pattern, they said, was “not close to statistical significance.”

“The moral is simple. We should be wary of claims—from all sides of the controversy—regarding turnout effects from voter ID laws based on current CPS data,” Erikson and Minnite concluded, referring to the Census Bureau data, known as the Current Population Survey, that the vast majority of studies of the question rely on.

“The problem is with the level of precision you can achieve with that kind of survey data and the complexity of variables you have to try to measure and control for in any given election,” Minnite explained to msnbc via email. “Multiple factors simultaneously push turnout up and pull it down, with different effects on different groups of people.”

To better understand what that means, consider a study often cited lately by defenders of voter ID. Conducted last year by Charles Bullock and M.V. Hood of the University of Georgia, the study sums up its conclusion in its title: “Much Ado About Nothing.” Bullock and Hood found that turnout in their state dropped by about a third of a percentage point from 2004 to 2008 after it instituted a photo ID requirement, but that white Georgians were in fact slightly more likely than non-whites to be affected.

But as other scholars quickly pointed out, comparisons between one election year and another are notoriously perilous: The 2008 election was unusual for featuring the first major-party African-American presidential candidate, and also because Georgia expanded early voting that year, both of which likely boosted minority turnout. Bullock and Hood tried to account for those factors and others that could have affected comparisons between the two years, but doing so is fraught with difficulty and introduces too high a level of uncertainty to produce reliable results, several experts said.

Barreto, of the University of Washington, went further, arguing that because of the methodological difficulties involved, looking at turnout is a misguided approach—which is why his research focuses simply on who does and doesn’t have an ID.

Turnout “doesn’t at all bear on the question of whether or not voter ID laws disenfranchise some voters,” Barreto said, “because turnout rates fluctuate for all sorts of reasons.”

Barreto, a principal at Latino Decisions, a Latino political research firm, thinks the tendency among some scholars to downplay the impact of voter ID reflects a blinkered worldview. “It’s because they’re not from the minority community or they didn’t grow up poor, and they don’t understand,” he said. “I think it does take some degree of, not advocacy, but interest in the topic to do the analysis properly.”

Not everyone agrees. “My sense is that the impact on turnout overall is likely to be very small,” Michael Hanmer, a political science professor at the University of Maryland who has looked closely at turnout issues, told msnbc, though he acknowledged that minorities and the elderly are disproportionately affected.

Are Other Vote Suppression Tactics More Effective?

The bottom line: We don’t have a clear picture of the impact voter ID laws have on turnout. But Tokaji, the Ohio State voting expert, said he worries more about other vote suppression measures: efforts to make voter registration harder, to purge voters from the rolls, or to pare back early voting, which African-Americans make disproportionate use of.

Consider Florida. After the state reduced early voting hours and days in most counties—it was restored in counties covered under Section 5—300,000 fewer votes were cast early last fall. In addition, in the roughly ten months after Florida imposed a law making it much harder for groups to register new voters, over 81,000 fewer Floridians registered to vote than during the equivalent period in the 2008 cycle, The New York Times found. Studies show that newly registered voters turn out at among the highest rates—a likely difference from those voters who lack ID.

Florida’s voter registration law was blocked by a court in September 2012. And after some Floridians waited as long as eight hours to vote, the state this year expanded early voting. But several other states, including Texas, Virginia, North Carolina, Wisconsin, and Arizona, are considering new efforts to go after early voting or voter registration.

Said Tokaji: “These restrictions on voting could ultimately have a greater impact on turnout than voter ID.”

What the Voter ID Studies Say:

Authors: Timothy Vercellotti and David Anderson, Rutgers Univ., on behalf of the U.S. Election Assistance Commission (2006)

Methods and Conclusions: The study used data from the Census Bureau’s Current Population Survey (CPS), as well as state and county data, from the 2004 election. It found a correlation between the strictness of a state’s ID requirement, and a decline in turnout, and found that the impact on minorities was greater than on whites.

Authors: David Muhlhausen and Keri Weber Sikich, the Heritage Foundation (2007)

Methods and Conclusions: The study attempted to replicate the Rutgers/EAC study after making what it said were improvements to the methodology. It found no correlation between voter ID laws and reduced turnout.

Authors: Michael Alvarez and Jonathan Katz, Caltech, Delia Bailey, Washington Univ. in St. Louis (2007)

Methods and Conclusions: The study used the CPS data, spanning the 4 elections from 2000 to 2006. It found that the most restrictive voter ID laws did reduce turnout, and disproportionately affected the poor and less educated.

Authors: Jason Mycoff and David Wilson, Univ. of Delaware, Michael Wagner, Univ. of Nebraska (2009)

Methods and Conclusions: The study used data from a Harvard survey spanning the 4 elections from 2000 to 2006, and ranked the strictness of a state’s ID requirement on a 1-6 scale. It concluded that voter ID laws did not significantly reduce turnout.

Authors: M. V. Hood III and Charles. S. Bullock III, Univ. of Georgia (2009) (not online)

Methods and Conclusions: The study used state data, and compared turnout in Georgia’s 2008 election, which required photo ID, with its 2004 election, which did not. It found a drop in turnout for Georgians lacking photo ID, and estimated that turnout would have been about one third of one percent higher without the photo ID requirement. But it found that racial minorities were no more likely than whites to be affected.

Authors: Robert Erikson, Columbia Univ., and Lorraine Minnite, Barnard College (2009) (not online)

Methods and Conclusions: The study examined the methodology used in the EAC/Rutgers, Heritage, and Caltech/Washington studies, and conducted its own analysis. It found that the relationship between the strictness of voter ID requirements and a decline in turnout was “not close to statistical significance,” and concluded that the currently available data does not allow for reliable conclusions to be drawn.

Research assistance by Maegan Vazquez