The Green Party candidate for Arizona's open U.S. Senate seat is dropping out of the race and has endorsed Democrat Kyrsten Sinema, 12 News reported Thursday.

It's unclear how Angela Green's departure from the race could affect turnout given the thousands of people who have already voted, but the Green Party candidate pulled in 138,000 votes in 2016, representing about 5.5 percent of the Senate vote that year. Green got about 400 votes during this year's primary election.

Sinema and her rival, Republican Martha McSally, are running neck-and-neck in a race that could help decide which party controls the U.S. Senate. The congresswomen are slugging it out for every single vote, and while Republican-affiliated voters have the early advantage, Democratic-affiliated voters are narrowing the gap, early returns from the Secretary of State's Office show.

Green, a political unknown who hadn't made a mark on the campaign trail this year, did not immediately respond to The Arizona Republic's request for comment. She says on her website she wanted to run to replace outgoing U.S. Sen. Jeff Flake because "I want to be the candidate I want representing me."

In 2016, there were about 2,500 early ballots cast by members of the Green Party. That party’s nominee ultimately collected nearly 139,000 votes, most of which came from voters from different parties. It is unclear if most of those votes were cast during early voting or on Election Day.

A spokesman for Sinema declined to comment on Green's endorsement.

Years ago, Sinema began her political career as a Green Party activist and anti-war activist. It is a time in her life that McSally and Republicans point to as evidence of a candidate who is too far-left to represent Arizona.

Sinema went on to serve in the Arizona Legislature in both the House and the Senate. Since winning a seat in Congress in 2012, she has brandished a centrist voting record.

Republic reporter Ronald J. Hansen contributed to this story.

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