PHOENIX — With one week left until Election Day, Democrat Kyrsten Sinema leads Republican Martha McSally by six points in head-to-head polling, according to a new NBC News/Marist poll.

In a poll that includes Green Party candidate Angela Green, Sinema's margin tightens to just three points.

Both polls are among Arizona's likely voters, and Sinema's leads in both polls are within the margin of error, which means this race is still a toss-up.

MCSALLY VS. SINEMA: Breaking down the Senate race

Respondents to a September version of the head-to-head poll had Sinema leading McSally 48-45.

As recently as Monday, though, RealClearPolitics had McSally leading Sinema by a small margin, so it appears this race will come down to the final days.

Sinema has been the subject of significant negative campaigning, from mushroom clouds to accusations of treason. Most advertising in support of Sinema has defended her rather than directly attacking McSally, a military veteran.

Both candidates have moved toward the right in their political careers -- Sinema is a progressive-turned-centrist and McSally has swung toward President Donald Trump's politics and rhetoric during this campaign.

McSally has raised $12.6 million to Sinema's $19.3 million, and each has seen more than $20 million spent in outside opposition advertising against them, according to ProPublica's Election DataBot.

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In the same NBC News poll, 32 percent of likely voters said they strongly approved of Trump's work as president, while 40 percent said they strongly disapproved. Only 7 percent of likely voters said they were unsure.

The NBC/Marist poll was conducted from Oct. 23-27.