In 2006, when the Republican State Leadership Committee was still a relatively obscure independent spending group with a good record of electing conservatives to state-level offices, the organization spent $20 million nationally. Four years later, the group spent about $30 million and was instrumental in flipping 22 state legislatures to GOP control. This election, the group expects to spend more than $37 million -- and to gain even more state legislatures, says president Matt Walter. “We have within our sights a supermajority within our majority, 66 of 99 chambers, which would be a modern Republican high.” They’re currently at 60.

The Republican State Leadership Committee (RSLC) is one of many national groups now vying for influence in state and local races, along with labor unions and organizations like Americans for Prosperity, the advocacy arm of billionaire conservatives Charles and David Koch. There’s no precise figure for how much outside influence in these races has accelerated, but as the rise of RSLC indicates, it’s been quite significant.

The influx of outside spending is the result of multiple factors, including the Supreme Court’s Citizens United decision and later rulings that have invalidated many state campaign contribution laws. But there’s also a growing sense among donors and activists that the best way to influence policy isn’t in idle, gridlocked Washington. It’s in statehouses and city halls.

This November, Democrats hope to chip away at Republican legislative majorities. But analysts are giving the 2014 advantage to the GOP, which is not only looking to bring Iowa under unified Republican control but also to win majorities in states with some Democratic control (Kentucky, Maine, New Hampshire) or dominant Democratic control (California, Colorado, Oregon).

The rise of this kind of spending has done more than nudge election results and flip state chambers, opponents say. Outside money has made campaigns nastier. It’s far easier to sling mud from 2,000 miles away, and the attack ads funded by national groups have become more viscerally negative. In a recent race for county sheriff in Maine, for example, voters heard a steady stream of radio ads faulting the incumbent for a mistake by an employee that led to an inmate sneaking out of her cell to have sex with another prisoner. The ads were paid for by a Florida man supporting the challenger.

RSLC in particular has taken flak for its work in North Carolina, where vulnerable Democrats were targeted with mailers in past years that have been criticized as playing to racial fears. The group has attracted less attention this year, although many in the state roundly criticized an RSLC-funded group for a May primary ad against a North Carolina Supreme Court justice that claims she “sides with child predators,” based on a 2010 dissent she wrote. One state politics reporter called it “perhaps the most despicable political advertisement ever aired in the state.”

Sometimes outside spending, which can’t be coordinated with official campaigns, can cause candidates headaches by taking control of messaging out of their hands. One Kentucky Democrat, for example, in 2012 received more than $100,000 in outside help in his bid to oust a Republican incumbent. But the ads run by those out-of-state groups were debunked by local press as distortions; the candidate they were supposedly helping wound up losing the election.

National groups say they’re merely providing more information in races that typically generate little interest. That’s good for democracy, they say. Still, many observers say outside spending will continue to result in increasingly negative state and local campaigns. “What I do know from our analysis of political TV ads in 2014 is that the majority of noncandidate ads are negative,” says Ben Wieder, a data reporter for the Center for Public Integrity. “While candidate ads still far outnumber noncandidate ads, the growing role of noncandidate spending in down-ballot races should mean more negative races.”