Arizona's Senate race is in a dead heat, with Rep. Martha McSally (R) narrowly leading Rep. Kyrsten Sinema (D) by 1 point, according to a new poll.

A Gravis Marketing poll found McSally ahead of Sinema 49 to 48 percent, a lead within the survey's 3.3-point margin of error. Three percent of voters are still undecided.

Monday's survey is the first one this year where McSally, who recently won a competitive three-way primary, is polling slightly ahead of Sinema, who didn't face a fierce primary fight.

According to the RealClearPolitics average of polling, Sinema has led McSally anywhere from 4 to 11 points in various polls this year. But with the general election officially starting, McSally is starting to close the gap with her Democratic opponent.

When voters are asked who they're "leaning towards" if the election were held today, McSally garners 23 percent of the vote, while Sinema takes 11 percent. But two-thirds of voters are still unsure.

The poll also tested President Trump's job approval numbers in a traditionally red state that he won by under 5 points in 2016. His numbers are underwater in Arizona, with 45 percent who approve and 52 percent who disapprove.

Arizona's Senate race is a top priority for both parties in the battle for the Senate. Republicans are looking to protect - and expand - their slim 51-49 seat majority. The party faces a favorable map, but has tough races even in states where Trump overwhelmingly won in 2016.

Republicans are hoping McSally can quickly put behind a nasty and costly primary battle in which her two opponents pulled her to the right. In the final days of the late August primary, McSally started to take aim at Sinema, characterizing her as too liberal for Arizona.

Democrats are hoping Sinema's head start in the race and large war chest can turn the state blue in a Senate race for the first time in nearly three decades.

Monday's Gravis poll was conducted from Sept. 5 to 7 and surveyed 882 likely voters in Arizona. The margin of error was 3.3 percentage points.