Like a recurring astronomical event, this year's election cycle features a once-a-decade confluence of term limits and redistricting -- a confluence that is expected to produce unusually high levels of turnover among state lawmakers.

The last time an election occurred in the wake of redistricting was 2002. That year, just under 24 percent of legislative seats changed hands in the November election, according to the National Conference of State Legislatures (NCSL). That was a higher rate than in any election cycle between 1998 and 2008, when the turnover ranged between 14.4 percent and 21.5 percent. (These numbers don't take into account turnover from mid-session vacancies and in states that have off-year elections; if these factors were included, it would likely increase the turnover rate.)

In isolation, redistricting and term limits have had significant impacts on turnover in the past. For instance, ever since the first term limits were implemented in California and Maine in 1996, states have sometimes seen extremely high rates of turnover in a single election cycle. In 1998, when term limits first hit the Michigan Legislature, a full 57 percent of the state House was term-limited out.

But the scale of what could happen in 2012 may be unprecedented. That's because this fall's elections will immediately follow another high-turnover election cycle -- the 2010 cycle, in which Republicans made widespread gains in state legislatures and produced a turnover rate of slightly less than 24 percent.

Putting two high-turnover cycles back to back could mean a record level of transition. "There's little doubt we will see a flood of new faces in the legislatures this fall," said Tim Storey, a political analyst with NCSL. "Come January of next year, it's quite likely that nearly half, if not more, of all state legislators will have only two years of experience or less."

The most obvious impacts will be in the 14 states that have adopted term limits and that hold legislative elections during even numbered years. Interviews with experts in these states suggest high rates of turnover this fall. Florida's Legislature could be one-quarter new in 2013, political experts in the state said. In Colorado, new members will account for at least one-third of the Legislature, depending on how many incumbents lose in November. The percentage of rookies in the California Assembly could be 40 percent or even as high as 50 percent, experts said. However, California's turnover rate could also be shaped by the state's new "top-two" primary system.

Term-limit states aren't the only places that are poised for high turnover. While North Carolina doesn't have term limits, the effects of redistricting could be substantial. An analysis by the nonpartisan North Carolina Center for Public Policy Research found that at least one-third of the Tar Heel State's legislators will be gone by next year.

Ran Coble, the group's executive director, suggested that turnover rates in the state Legislature could eventually approach or exceed record levels from the 1970s. The reasons? "Retirements, runs for higher office, accepting other jobs and, most of all, redistricting," Coble wrote in the report.

But in most cases, voters remain in favor of term limits. For instance, in Colorado, "a majority of voters still love [them]. Indeed, whatever goes wrong in the General Assembly seems to reinforce the idea that legislators should be term-limited," said John Straayer, a Colorado State University political scientist.

To be fair, there have been some fruitful effects from enacting term limits. For instance, the increased churn of lawmakers has likely drawn candidates into the fray who otherwise might not have tried to run.

"Following the implementation of term limits, many states have seen an increase in the number of minorities, women and people holding elected office," said Dan Roth, communications director for the Democratic Legislative Campaign Committee. "Adding new legislators can [create] opportunities for new ideas and fresh thinking."

In addition, term limits have encouraged the process of making legislatures more reflective of their state's political leanings. For instance, as voters in Louisiana and Oklahoma have turned increasingly Republican in recent years, term limits have weakened the hold of long-serving Democratic legislators and allowed control of the chambers to pass to the GOP.

But there are longstanding concerns about how term limits have shaped - and could continue to shape -- the operations and effectiveness of legislatures. Here are a few of them:

A loss of institutional memory. Less-experienced lawmakers are more apt to find themselves reinventing the wheel, wasting time and effort that could have been avoided if they'd had better institutional memory. Meanwhile, wherever lawmakers are short on expertise, unelected officials such as aides and lobbyists can grow in influence.

"The overall length of service has not changed much, but the 10 to 20 percent of legislators who formerly were the keepers of institutional memory and respect -- and those who were the substance and process mentors for the newly elected -- are gone," said Straayer of Colorado State.

Ken Warren, a political scientist at Saint Louis University in Missouri, said that by the time lawmakers "start really mastering the system, they are termed out. It discourages good people from running, since they know that in a few years they will be gone."

In the absence of policy and procedural experience among lawmakers, partisanship and ideology can fill the void.

"The loss of institutional knowledge has been palpable and dispiriting," said Jan Moller, a former statehouse reporter in Baton Rouge and now director of the Louisiana Budget Project. "The Legislature is far more partisan and ideology-driven than before term limits hit. It is becoming a lot more like Washington -- and I say that with all the disdain I can muster."

Solidification of dominant parties. Initially, term limits helped minority parties by clearing out longstanding majority-party incumbents, thereby opening up previously uncontestable seats. But eventually, term limits may end up reinforcing a state's majority party. That's because minority parties -- especially those in small-population states -- may find it hard to produce enough credible candidates to replace those from their party who are term-limited out. Majority parties in these states would have a much easier time.

Rapid ascension to leadership positions. In Nevada, there will be four new leaders in each chamber next session, said Las Vegas-based political analyst Jon Ralston. In California, there has been so much leadership turnover in the Legislature in recent years that "I joked the other day that pretty soon California will have more ex-legislators than people who used to work at McDonalds," said Democratic strategist Garry South.

A study of the impact of term limits by NCSL, the Council of State Governments and the State Legislative Leaders Foundation concluded that in term-limited legislatures, "it is common to see members begin their campaign for leadership in their freshman year."

For instance in Florida, freshman lawmakers "begin to lobby their colleagues for support for leadership and often lock up the speakership seven years ahead, after completing just one year of their first term," said Aubrey Jewett, a political scientist with the University of Central Florida. "This has not always resulted in accomplished legislators rising to the top, since who can really tell who will be effective after just one year in office? Rather, it is ideology and personality and the ability to raise money in one's first year that seem to be the deciding factors."

Such dynamics pose leadership challenges on several levels. From day one, new legislators are looking after their careers, rather than learning the procedural and substantive ropes. Then, once they take over as a leader, they lack the depth of experience that their pre-term-limit predecessors had. Finally, once in office, they quickly become lame ducks, limiting their leverage to put their legislative priorities into effect.

Similar problems arise for committee chairs, the term-limits study found. "In some term-limited legislatures, committees are chaired by legislators who have no previous experience on the committee or, in a few cases, no previous experience in the legislature," the report said.

Meanwhile, lawmakers who know their time in a chamber is short may have a short-term, careerist orientation. Sometimes this means making a big splash quickly to jump-start their political career. "Term limits have enhanced the ambition and provincialism in legislators, since they are constantly thinking about the higher office or the return to their home communities," said Jay Barth, a political scientist at Hendrix College in Arkansas.

In other cases it may mean ditching a legislative career prematurely to take an appointed position in state government. That has happened twice recently in Ohio.

The loss of working partnerships. The longer one serves with the same colleagues across the aisle, the bigger the penalty for demonizing them or operating in bad faith. Under term limits, aggressive tactics and less cooperation may flourish.

Oklahoma-based political scientist Rick Farmer, a fellow at the Ray C. Bliss Institute of Politics at the University of Akron, refers to the "grease" in the gears of lawmaking.

"Term limits sever relationships," Farmer said. "Relationships are the grease in the cogs of the legislative process. Without grease the machine still functions, but there is a lot more heat and noise. Without relationships, everyone in the Capitol -- from journalists to lobbyists to staffers to members to citizens -- must work harder to get the job done."

Former Colorado state Rep. Gayle Berry, a Republican who is now a lobbyist, recently lamented to the Denver Post about the impact of term limits on bipartisanship. "The biggest thing over the years has been the change in statesmanship," Berry told the paper. "Some of the lawmakers who had worked with governors in a different party worked in a more bipartisan manner."

If these trends have been playing out due to term limits over the past decade and a half, the sheer scope of the turnover in the 2012 elections could make the impact bigger than ever.