Sen. Mark Begich (D-Alaska) aired a television ad earlier this summer linking himself to Sen. Lisa Murkowski (R-Alaska). It featured an aviation businessman touting their similarities and saying, “I don’t think we should break up that team.”

The problem: Murkowski, naturally, is backing Begich’s Republican opponent, Dan Sullivan. And now, she’s making it crystal clear whose team she's on.

The Sullivan campaign is going on the air this week with a new ad, obtained Tuesday morning by The Washington Post, that features Murkowski looking into the camera and endorsing Sullivan.

“I need a partner in the Senate who will work to defend Alaska’s interests, not the Obama agenda,” says Murkowski, one of the state’s most popular elected officials. “Alaska needs Dan Sullivan.”

The Alaska Senate contest is considered a toss-up, and could help determine which party controls the Senate.

In the new ad, Murkowski says, “We’re all tired of the negative ads, and I’m especially disappointed by the dishonest attacks on Dan Sullivan.”

Murkowski does not mention Begich, but the context is clear. The Begich campaign has been running a series of ads attacking Sullivan, including one that accused Sullivan, a former state attorney general, of letting sex offenders get off with light sentences. The campaign pulled the ads following demands from a crime victim’s family.

In the new ad, Murkowski defends Sullivan’s record. “As our attorney general, Dan protected women from domestic violence and sexual assault,” she says.

Considering the dismal public approval of Congress, not many campaigns this year have aired ads featuring other politicians offering endorsements.

The Sullivan ad with Murkowski is an exception, as is an ad Republican Senate nominee Scott Brown ran in New Hampshire featuring Sen. Kelly Ayotte (R-N.H.). In both cases, male candidates are hoping Republican women senators can help them broaden their appeal to women and independent voters.