Arizona Democrat Mark Kelly and incumbent Sen. Martha McSally Martha Elizabeth McSallyOn The Trail: Making sense of this week's polling tsunami The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE (R) are virtually tied in the Grand Canyon State’s 2020 Senate race, according to a new Emerson College poll released Tuesday.

Kelly, a former astronaut and gun control activist who's married to former Rep. Gabrielle Giffords (D-Ariz.), has the support of 46 percent of registered voters, while McSally, who was appointed to her position after losing the race for Arizona’s other Senate seat last year, has 45 percent.

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Despite the poll showing a tight race overall, it does flash a warning light for McSally, who trails Kelly among independents by 5 points.

The race between Kelly and McSally is one of the nation’s highest profile Senate races. It's also McSally’s second Senate campaign in two years — last year she lost a bid against Democrat Kyrsten Sinema to replace retiring Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeHow fast population growth made Arizona a swing state Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden MORE (R), but was eventually appointed to fill the Senate seat left open after the death of former Sen. John McCain John Sidney McCainCrenshaw looms large as Democrats look to flip Texas House seat Analysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture MORE (R-Ariz.).

The Arizona race is also likely to be one of the costliest of the 2020 cycle. So far Kelly has outpaced McSally in fundraising in every quarter this cycle, ending the third quarter of 2019 with $9.5 million in cash on hand compared to McSally’s $5.6 million.

The 2018 race between Sinema and McSally drew $48 million in spending between the two candidates and outside groups. Only five other contests attracted more spending that year.

“The support that we’re seeing for this Mission for Arizona is simply out of this world,” Jen Cox, Kelly's campaign manager, said after the campaign’s third quarter haul was announced.

“The past few months, Mark has been talking with Arizonans from Window Rock to Clarkdale to Parker about solutions to tackle rising health care costs and the price of prescription drugs," she continued. "This campaign is demonstrating the power of putting Arizona first, not corporate PACs and not divisive politics.”

Unseating McSally would significantly ease Democrats’ path to winning the Senate majority: The party has to flip three seats if it also takes the White House and four if it does not.

The Cook Political Report, a nonpartisan election handicapper, rates the race as a “toss up.”

The Emerson College poll surveyed 901 registered voters from Oct. 25-28 and has a margin of error of 3.2 percent.