Most of the political world’s attention this year will be focused on the presidential race. But while the nation is watching President Obama and Republican presidential candidate Mitt Romney duke it out, state legislatures will be forging their own battles -- all the more important because of the influence that state governments have had in recent years on hot-button issues ranging from voter identification to hydrofracking regulations.

This year’s state legislative contests are being shaped by a one-two punch: a historic shift of 20-plus chambers in the GOP’s direction on Election Day 2010, followed by a once-every-decade process of redistricting. In a strategic sense, the GOP timed its big 2010 gains perfectly since line redrawing has allowed the party to protect them.

That being said, this year’s legislative elections will likely be either a slight reinforcement of GOP gains or a small rollback by the Democrats. But a big move in either direction seems unlikely at this point, particularly given the close presidential race.

This is the first in a series of articles handicapping the 50 state legislatures leading up to the 2012 election. The assessment is based on interviews with dozens of state and national political sources. As always, we rate chambers on the following scale: safe Republican, likely Republican, lean Republican, tossup, lean Democratic, likely Democratic and safe Democratic. The categories labeled “lean” and “tossup” are considered competitive or in play. Chambers in either of the “likely” categories are not expected to change party control on Election Day, but it’s possible that the minority party could net a few seats and nibble into the majority’s lead.

This year, we find a total of 24 state legislative chambers to be in play -- 28 percent of all chambers holding elections this year. Nine chambers lean Republican (eight of them are currently held by the GOP and one is tied). Eight chambers are tossups (five are held by the Democrats and three by the GOP). And seven chambers lean Democratic (five are held by Democrats, one by the GOP and one is tied).

To have two dozen chambers in play at this stage of the 2012 cycle is somewhat above historical norms, but not as high as the landmark year of 2010. Two summers ago, it was already clear that 2010 was going to be a cycle of historic volatility, with 27 chambers, or 32 percent, in play during our summertime attempt at assigning ratings.

But the big difference between 2010 and 2012 is the partisan split of these in-play chambers. At this point two years ago, it was plain to see that the GOP was poised for one-sided gains: 21 Democratic-held chambers were in play in our first rating, compared to just four Republican-held chambers. This meant that the Republicans could go on offense all across the nation without having to worry about playing much defense.

That partisan imbalance was historically unusual: In the previous four election cycles we handicapped, the typical ratio of vulnerable chambers between the parties was close to even. And this year, it is again.

This year, 12 Republican-held chambers are in play, compared to 10 Democratic-held chambers and two tied chambers. In the absence of a strong partisan wave, this would suggest a possible net shift of between zero and two seats in either party’s direction on Election Day. An outcome in that range would solidify -- or at most, roll back slightly -- the GOP’s gains from 2010.

How big were those gains from 2010? Very big. The GOP now controls 59 legislative chambers, the Democrats control 37 and two are tied. Nebraska has a unicameral, nonpartisan legislature. (A full breakdown of current margins in each of the state legislatures is provided courtesy of the National Conference of State Legislatures.)

If our ratings prove accurate, then even if the Democrats manage to seize a few chambers away from the Republicans in 2012, they will still find themselves far behind the GOP in overall control of chambers on Election Night, and quite possibly for more election cycles beyond that.

Structurally, the Democrats’ long-term hole is worsened by a half-dozen chambers that shifted to the GOP in 2010 and that are unlikely to return to the Democratic fold a generation or more. These include both chambers in Alabama, both chambers in North Carolina and the state House in Indiana and Montana.

The Democrats also have new realignment worries for 2012. This year, the party is at risk of losing both chambers in Arkansas (we rate both as tossups), as well as the officially tied but de facto jointly controlled Alaska Senate (lean Republican) and the Kentucky House (lean Democratic). Once the Democrats lose these chambers, none will easily return to the Democratic fold, given the long-term partisan trends in each of these states.

Perhaps the most immediate disappointment for the Democrats is the Republicans’ seeming ability -- for now, anyway -- to defend their gains from 2010 in swing or Democratic-leaning states. Eight chambers seized by the GOP in 2010 and rated lean Republican come in states Obama won in 2008: Maine (Senate), Michigan (House), Minnesota (Senate), New Hampshire (both chambers), Ohio (House), Pennsylvania (House) and Wisconsin (Senate). To make significant gains, the Democrats have to put more of these chambers into play.

The Democrats do have some opportunities to play offense. Their best chances for flipping a chamber back two years after losing control are probably the Colorado House, the Minnesota House and the New York Senate (all of which we rate as tossups) and the Maine and Oregon houses (both of which are rated lean Democratic).

We’ll continue to analyze ongoing developments in the state legislatures as the election season progresses. Click a state in the map below to view our chamber-by-chamber ratings for each state.

State Legislature Control: U.S. Totals

Rating  Held by D Held by R Currently Tied Total
Lean Republican 0 8 1 9
Tossup 5 3 0 8
Lean Democrat 5 1 1 7
Total 10 12 2 24

Select Map:
Democratic Majority
Republican Majority
State Elections

Having a majority of seats in play in a year when many states have newly-drawn districts could greatly change the composition of statehouses. Will Republican state legislators be able to hold and extend their reach? Could Democrats regain some of the losses handed to them in 2010? Governing’s team of writers and contributors will monitor developments all the way up to Election Day and beyond.

Click a state in the above map to display current breakdowns for each state legislature.

Information is current as of June 2012.