WASHINGTON — Arizona’s closely watched Senate race is a statistical tie, according to a new NBC News / Marist College poll that shows Democrat Kyrsten Sinema leading Republican Martha McSally by three points with likely voters, within the poll’s margin of error.

The poll finds Sinema garnering 48 percent support from Arizona likely voters in a two-way contest, while McSally has the backing of 45 percent.

Among all registered voters, it’s a similar margin at 47 percent for Sinema, 44 percent for McSally. That result shows that the race has tightened since June, before McSally clinched the GOP nomination. At that time, Sinema led McSally among registered voters, 49 percent to 38 percent. (NBC News did not calculate a likely voter model for its June survey.)

When Green Party nominee Angela Green is noted as an option on the Senate ballot, Sinema’s edge with likely voters slips to 45 percent to McSally’s 43 percent, with Green winning the support of six percent of voters.

In the head-to-head contest among likely voters, Sinema leads with independents (52 percent to 38 percent), white college graduates (54 percent to 42 percent), Latino voters (54 percent to 33 percent), voters under 30 (66 percent to 25 percent) and women (53 percent to 38 percent).

McSally’s strongest supporters include Trump backers (86 percent to 8 percent), men (53 percent to 41 percent), and whites without a college degree (53 percent to 40 percent).

Among whites, the two are nearly tied at 47 percent for Sinema and 48 percent for McSally.

Overall, Sinema enjoys higher favorability numbers than her GOP rival, who endured a difficult primary contest from two GOP candidates who ran to her right. Forty-six percent of Arizona likely voters have a positive view of Sinema, compared to 33 percent who view her unfavorably. For McSally, on the other hand, just 40 percent view her favorably and 42 percent view her unfavorably.

More voters also disapprove of President Donald Trump’s performance than approve of it. Among likely voters, 44 percent approve of the job Trump is doing, while 51 percent disapprove. Among all Arizona adults, it’s 39 percent approve, 50 percent disapprove. That’s compared with 39 percent of all Arizona adults who approved of Trump in June, while 47 percent disapproved.

And asked if they would prefer a Congress controlled by Democrats or one controlled by Republicans, 47 percent of likely voters say they prefer Democrats, while 44 percent choose Republicans.

Likely voters are also more likely to say they want their vote to send a message in favor of more Democrats to be a check and balance on Trump (52 percent) than to be a message in favor of more Republicans to help Trump pass his agenda (38 percent).

While the Senate race is too close to call, incumbent Republican Gov. Doug Ducey leads Democratic challenger David Garcia among likely voters by eight points in a two-way race, 51 percent to 43 percent.

Among registered voters, it’s a similar margin, with 51 percent for Ducey and 42 percent for Garcia.

Ducey, who has had to navigate a complex political environment in Arizona — particularly on education and immigration issues — remains popular, with 51 percent of likely voters giving him a favorable rating while 39 percent disagree.

Forty-two percent have a favorable view of Garcia, while 35 percent have an unfavorable one and 24 percent say they don’t know enough to have an opinion.

The poll of 950 Arizona adults was conducted September 16-20, 2018. The margin of error for all adults is +/- 3.7 percent. The margin of error for 763 registered voters is +/- 4.2 percent. The margin of error for 564 likely voters is +/- 4.7 percentage points.