The Democratic Senatorial Campaign Committee is going up with a $526,000 weeklong ad buy in support of Arizona Senate nominee Richard Carmona.

The money is set to cover this week only and is part of the first independent expenditure the committee has made in the race.

Carmona, a former surgeon general, faces Rep. Jeff Flake (R) in what has become a competitive race. The Washington Post first reported the news of the DSCC’s move.

Carmona has spent heavily on advertising in September in an effort to define himself in a positive light. According to a recent Carmona internal poll, he has narrowed the race’s margin.

But the next couple of weeks are crucial to the trajectory of this race. Early voting is only nine days away, and Flake just went up with negative advertising against Carmona. Outside groups are also expected to jump into the race to support Flake. Politicos are watching closely to see how Carmona holds up against the barrage.

Another factor could also come into play — there has been increasing chatter, but no hard evidence, that President Barack Obama’s campaign is eyeing Arizona as a place to expand its playing field.

“We are always looking, always looking for opportunities, and, you know, we’re heartened by what we see, not just in these battleground states, but some of the states that weren’t battleground states,” Obama senior adviser David Axelrod said when asked by CNN’s Candy Crowley on Sunday whether he was looking to play in Arizona.

“But I’m not going to — I can’t tell you today exactly how we’re going to expend our resources in the final 30 days,” he added.

It is unclear how this would affect the race. In other states, including Wisconsin, Obama’s performance has helped Senate candidates. But a major point of attack Flake has made against Carmona has been to tie him to the president.

Roll Call rates the Senate race as Leans Republican. This is an open-seat race to replace retiring Sen. Jon Kyl (R).