Republicans have the opportunity to take control of a record number of state legislative chambers across the country this year, as Democrats play defense in unfavorable terrain.

The Republican landslide in 2010 and the subsequent redistricting process in 2012 gave the GOP control of a nearly unprecedented number of legislative chambers. Today, the party controls 59 of the 98 partisan chambers in 49 states, while Democrats control only 39 chambers (One legislature, Nebraska’s is officially nonpartisan).

Once election results are tabulated in the 6,049 legislative races on the ballot in 46 states this year, Republicans could find themselves running even more.

If Iowa Democrats can’t hang on to control of the state Senate, Gov. Terry Branstad (R) will be freer to pursue an ambitious agenda. If Arkansas Republicans keep control of the state House and win the governor’s mansion, the future of that state’s unique approach to Medicaid expansion under the Affordable Care Act is at risk. In Kentucky, Sen. Rand Paul (R) could take advantage of a Republican state legislature to change a law that prevents him from running for president and re-election to the U.S. Senate at the same time.

State legislative elections, in which candidates raise little money and generate almost none of the attention given to more prominent contests for U.S. Senate or governor, are especially susceptible to national political trends. In 2010, Republicans picked up more than 700 seats, which amounted to nearly one in 10 legislative seats around the country.

This year, another legislative wave benefiting the GOP is certainly possible, perhaps even likely.

Voters deeply disapprove of President Obama, with a Washington Post-ABC News poll published this week finding just 43 percent approve of his job performance. Those polled say they would favor a Republican candidate for Congress over a Democrat by a 50 percent to 44 percent margin.

And history argues for GOP gains: In 26 of the 28 midterm elections held since 1900, the party that controls the White House has lost seats.

“For Republicans, the main message point everywhere is, it’s about Obama. There’s not a lot of creativity there,” said Michael Sargeant, executive director of the Democratic Legislative Campaign Committee. “It’s a difficult political environment”

States like New Hampshire, which is closely divided between the two parties, are especially susceptible to national waves. The 400-member state House there, the largest legislative chamber in the nation, has swung wildly in recent years. Democrats control 212 seats today — one of the most vulnerable majorities in the country.

In Washington State, where the Senate majority is controlled by a combination of Republicans and two centrist Democrats, the GOP is poised to gain at least one seat, formally giving them a total majority.

Nevada Democrats control the state Senate by the slimmest possible margin: 11 seats to 10. Republicans, led by popular Gov. Brian Sandoval (R), have poured millions of dollars into building a field operation aimed at retaking the chamber, and early vote numbers show the GOP has made impressive gains that put the chamber at risk.

In other states, Democrats are defending seats in areas that have changed ideologically. The West Virginia state House, where Democrats hold a 53 to 47 seat majority, is in play as President Obama’s approval rating sinks ever lower among white voters in coal country. And Democrats are defending a 54 to 46 seat majority in the Kentucky state House.

As Washington stands mired in partisan gridlock, states have undertaken a nearly unprecedented legislative boom. Experts say that’s because so many states are controlled by one party, giving that party free reign to pass ambitious liberal or conservative agendas.

“The states have been pushing the envelope from all directions, and sometimes counter-intuitively,” said Tim Storey, a legislative analyst at the National Conference of State Legislatures. “Immigration, minimum wage, tax increases, tax cuts, environmental legislation, abortion rights, all of those things, you’ve had a real uptick in policy making at the state level.”

But going too far can risk a backlash from voters who want to chart a more moderate path.

Colorado Democrats passed ambitious gun control legislation after taking control in 2012, but voter backlash allowed Republicans to successfully recall two sitting Democratic senators, including the Senate president. Now, Democrats cling to a narrow 18 to 17 seat majority, and Republicans have high hopes for winning back several seats.

“Colorado is a fairly evenly split state, so there’s not a lot of margin there for railroading some extreme policies,” said Bill Cadman, the Republican minority leader of the Colorado Senate. “The trend looks favorable to Republicans. People are generally dissatisfied with the direction the country is going, and whoever is driving that is responsible.”

Democrats have their own opportunities to win back contested chambers.

In the Arkansas House, Republicans control 51 of 100 seats. If Democratic efforts to turn out new voters pay dividends, that chamber is in play. The party is driving turnout in Iowa, where a closely fought U.S. Senate race is coming down to the wire; Republicans control the state House 53 seats to 47, a margin close enough to be at risk. And Pennsylvania Gov. Tom Corbett (R) trails his Democratic opponent badly in recent polls, putting the GOP’s four-seat Senate majority in play, too.

Still, the national atmosphere has Republicans optimistic they can set new records. The GOP controlled legislatures in 30 states after the 1920 elections, Storey said, their modern high-water mark. Before Election Day 2012, Republicans controlled 62 legislative chambers. To match those marks, the party would need to take control of three chambers — perhaps in New Hampshire, Iowa, Nevada or Kentucky.

If there is a silver lining for Democrats, NCSL’s Storey said, it’s that successively bad midterm elections have the party near its nadir. Ambitiously conservative agendas in states like North Carolina, Georgia and Virginia, all states where Republicans have made recent gains, put Democrats in a position to begin targeting winnable seats once more.

“Whichever state legislative chambers Republicans fail to pick up this Election Day are likely out of the GOP’s reach for a decade,” said Carolyn Fiddler, a Democratic strategist who focuses on legislative seats at The Atlas Project. “Republicans will make their hay while the sun shines this year, but it could be their last chance to do so for quite some time.”