The outcome of this year's mid-term elections will determine whether Republicans will take control of the U.S. Senate and thus both chambers of Congress, as the GOP is expected not only to maintain power in the House but to gain as many as eight seats.

To take the Senate from the Democrats, Republicans need to pick up six seats in November. They're getting help from the nation's electric utilities, including the largest: North Carolina-based Duke Energy. At a time when the industry is facing critical federal regulatory issues, Duke Energy has shifted its support to the group dedicated to electing regulation-averse Republicans to the U.S. Senate and away from its Democratic counterpart.

According to the Center for Responsive Politics' OpenSecrets.org database, Duke Energy's political action committee cut its contributions to the Democratic Senatorial Campaign Committee over previous election cycles. So far this cycle, Duke has given the DSCC $10,000. That's down from $11,000 in 2012, and it's a sharp reduction over the last mid-term elections in 2010, when the company gave the DSCC $22,500.

At the same time, Duke Energy's PAC has reportedly contributed $30,000 to the National Republican Senatorial Committee so far this election cycle -- a level of giving by the company that's held steady for every cycle since 2006.

Duke Energy's shift in giving toward a Republican Senate follows the general trend in partisan contributions among electric utilities, which so far this election cycle have given 62 percent of their contributions to Republicans, according to OpenSecrets.org. That represents a partisan switch from the last mid-term election cycle in 2010, when 55 percent of the industry's contributions went to Democrats.

Duke Energy has also shifted its individual contributions away from Democrats in recent election cycles. So far in 2014, 43 percent of the company's contributions in U.S. Senate races have gone to Democrats, compared to 49.5 percent in 2012 and 55 percent in 2010.

Since then, President Obama's Environmental Protection Agency has proposed new rules to curb carbon dioxide emissions from power plants, which Duke Energy and the wider industry have opposed. Republicans have been outspoken critics of the EPA rules, arguing that they hurt the energy industry and raise prices for consumers.

Another issue of concern to electric utilities is regulation of coal ash, which has been a pressing problem for Duke Energy in the wake of a February spill into the Dan River from one of its shuttered North Carolina coal plants. The EPA is scheduled to release final federal rules for coal ash disposal in December. Since those rules were first proposed in 2010, the Republican-controlled House has voted to take away the EPA's authority to regulate coal ash, but those efforts have been blocked in the Democratic-controlled Senate.

Electric utilities show love for Louisiana's Landrieu

But one Democratic senator up for re-election is enjoying strong support from electric utilities including Duke Energy: U.S. Sen. Mary Landrieu of Louisiana, who is facing the toughest challenge of her career.

Landrieu is the second-biggest recipient of contributions from the electric industry among all members of Congress during this election cycle after Republican House Speaker John Boehner of Ohio. So far, she's received $299,451 to Boehner's $364,200, according to OpenSecrets.org. Landrieu is also the Senate's seventh-biggest recipient of contributions from Duke Energy, with her campaign having received $5,500 so far this cycle from the company's PAC.

Landrieu chairs the Senate's powerful Energy and Natural Resources Committee. Should she lose but Democrats continue to hold the Senate (and at least one respected prognosticator thinks a Democratic Senate is possible), the likely new chair of that committee would be Sen. Maria Cantwell (D-Washington). Cantwell is a strong supporter of environmental regulations, having received a lifetime score from the League of Conservation Voters of 90 percent. That compares to just 51 percent for Landrieu, whose score is below the U.S. Senate average of 57 percent.

Landrieu, who is also a favorite of the oil and gas industry, has taken anti-regulatory positions even more extreme than the utilities at times. For example, she held an event drawing attention to her opposition to the EPA's carbon limits at the Big Cajun II in Louisiana, one of the nation's most heavily polluting power plants. It's operated by New Jersey's NRG Energy, whose CEO has said he believes the EPA should regulate his industry's carbon pollution.

Earlier this month, U.S. Sen. Joe Manchin, a West Virginia Democrat, said energy-producing states like his would be "absolutely dead" without Landrieu.

Landrieu is running for re-election to a fourth term in a nonpartisan blanket primary on Nov. 4 against four other Democrats and three Republicans, including U.S. Rep. Bill Cassidy and Tea Party-based former Air Force officer Rob Maness. If no candidate receives 50 percent plus one vote, a runoff between the top two candidates will be held on Dec. 6.

Utilities like Pryor, McConnell; Hagan not so much

Louisiana is considered one of the six states that could swing the Senate. Besides Alaska, the other key senatorial swing states are all in the South. Here's a look at utility contributions in those races:

* Arkansas. Duke Energy's PAC has contributed $6,000 so far this election cycle to Sen. Mark Pryor, the incumbent Democrat. Overall, electric utility PACs have contributed $118,250 to Pryor this cycle, making the industry his 13th-biggest industrial contributor. Electric utilities are not among the major contributors to Pryor's Republican opponent, U.S. Rep. Tom Cotton, nor were they among the top contributors to Cotton's 2012 U.S. House campaign.

Along with Landrieu and Sen. Mark Begich of Alaska, Pryor is one of 15 Democratic U.S. senators who joined with 30 of their Republican colleagues in signing a letter asking the EPA to delay carbon emission rules.

* Georgia. This race pits Republican businessman David Perdue against Democrat Michelle Nunn, CEO of the nonprofit Points of Light, for the seat being vacated by retiring Sen. Saxby Chambliss, who was among the top congressional recipients of electric utility support during his last re-election campaign in 2008. Electric utilities have not been a major contributor in this year's race between Perdue and Nunn, according to OpenSecrets.org.

Perdue has spoken out forcefully against the EPA's power plant carbon rules. Nunn has made non-commital statements about the EPA rules, but she has called for addressing climate change and shifting to cleaner energy sources.

* Kentucky. So far electric utilities have contributed at least $157,550 to U.S. Sen. Mitch McConnell, the incumbent Republican and Senate minority leader, including $500 from Duke Energy's PAC. That makes him the industry's sixth-biggest beneficiary in this cycle. McConnell has been an outspoken critic of the EPA and has led the fight against carbon rules for power plants.

Electric utilities are not major contributors to McConnell's Democratic opponent, Kentucky Secretary of State Alison Lundergan Grimes, though she has also run on a pro-coal platform and has accused President Obama of "attacking" Kentucky's energy industry.

* North Carolina. In its home state, Duke Energy's PAC has not contributed so far to either incumbent Sen. Kay Hagan, a Democrat, or her Republican opponent, state House Speaker Thom Tillis, according to OpenSecrets.org. Electric utilities are not a top industrial donor in the race, though employees of Duke Energy and their families have contributed over $21,000 to Hagan's campaign.

Hagan has said she supports carbon rules for power plants, though she has called on the EPA to delay them. As a state senator, she co-sponsored North Carolina's Clean Smokestacks Act, which required utilities to do a better job of cleaning air emissions -- though consequently that led to more toxic coal ash.

Tillis has targeted Hagan for being weak on coal ash, pointing out that she voted for a bill that exempted coal ash waste pits from stricter regulations. She has also faced criticism from the North Carolina press for calling for more study of coal ash in the wake of the Dan River spill rather than for strong regulatory action.

Meanwhile, Tillis has emphasized his leading role in crafting state legislation to establish new rules for coal ash in the wake of Duke Energy's spill, though environmental advocates have been critical of that legislation for being soft on Duke while leaving North Carolina waters vulnerable to contamination.

Tillis has a lifetime score from the LCV of 26 percent, including a 2013 score of 0. Hagan has a lifetime score of 84 percent.