Democratic National Committee chairwoman Debbie Wasserman Schultz on Sunday dismissed the potential political impact of a delayed decision on the Keystone XL pipeline, calling it a "complex" decision that will need to be carefully weighed.

The State Department, which has been reviewing the environmental impact of a proposal to build an oil pipeline from Canada to refineries along the Gulf Coast, announced this week that it would postpone its decision on whether to approve the project.

Some Republicans who support the project accused Democrats and the White House of purposefully pushing back a ruling until after this year's midterm elections -- but Wasserman Schultz attempted Sunday to dismiss such a notion.

"The decision over the Keystone pipeline is complex and it has to be examined very carefully," Wasserman Schultz said on NBC's "Meet The Press." "It affects multiple states."

Because of the weight of the issue, Wasserman Schultz said, she wants "to make sure the right decision is arrived at and the president makes that decision carefully and doesn't put politics in his decision."

"[President Obama] has to continue to take a close look at it," she added. "The environmental concerns are legitimate."

The issue has become a puzzling one politically for Democrats during this challenging election cycle. On the one hand, some of the most vulnerable incumbent Democratic senators, including Sens. Mary Landrieu, D-La., and Mark Begich, D-Alaska, are running for re-election in states where energy policy is of paramount importance, and where approving Keystone could provide an important boost.

But many Democrats will also rely on big donations from powerful environmentalists who staunchly oppose construction of the pipeline, including billionaire Tom Steyer.

With their Senate majority hanging in the balance, and facing a challenging Senate map, Democrats will also need to contend with public approval for Obamacare and with the president's own stagnant approval rating. But, Wasserman Schultz contended in her interview Sunday, the individual candidates will be of more importance to voters than either of those national issues.

"These elections, particularly the Senate elections, are referendums on the candidates running," Wasserman Schultz said.

Those Democratic candidates, particularly the most vulnerable, will likely receive an assist on the campaign trail from a cast of high-profile Democrats, including former President Bill Clinton, who has already campaigned in Kentucky for Democrat Alison Lundergan Grimes.

Whether Clinton's wife, Hillary Clinton, will step out in 2014, however, remains an open question, particularly as she balances the demands of the midterm election with her own political considerations for 2016, when she might run for president.

"I'm confident Hillary Clinton is going to be helpful to our candidates across the country," Wasserman Schultz said.