Former President George W. Bush and Utah Senate candidate Mitt Romney Willard (Mitt) Mitt RomneyBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power The Memo: Trump's strengths complicate election picture MORE are scheduled to visit Arizona in the coming weeks to boost Senate candidate Rep. Martha McSally Martha Elizabeth McSallyThe Hill's Campaign Report: Presidential polls tighten weeks out from Election Day Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' New ABC/WaPost poll finds Trump edging Biden in Arizona, Florida MORE (R-Ariz.), who is locked in a tight race.

The Arizona Republic reported that the two prominent Republicans will make separate trips to fundraise for McSally and the GOP in an effort to bolster support among more moderate Republicans.

Romney, the 2012 presidential nominee who is running to replace retiring Sen. Orrin Hatch Orrin Grant HatchBottom line Bottom line Senate GOP divided over whether they'd fill Supreme Court vacancy MORE (R-Utah), is expected to headline a rally Friday. Romney, who is Mormon, will stump for McSally in the state's East Valley, which has a large Mormon population, The Arizona Republic reported.

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Bush will head to the state on Oct. 19 to host a private fundraiser in Scottsdale, the news outlet reported. Attendees must contribute $2,700 per person to attend the event and $5,000 for a photo with the former president.

McSally is squaring off with Rep. Krysten Sinema Kyrsten SinemaReplacing Justice Ginsburg could depend on Arizona's next senator Why Trump, GOP are running into trouble in Arizona Gun control group to spend at least million in Arizona ahead of November MORE (D-Ariz.) in the race 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-Ariz.). A CBS News poll released Sunday showed the Democrat with a 3-point advantage in the race, though the difference fell within the poll's margin of error, making it a statistical dead heat.

Polling out Wednesday showed McSally gaining ground as the election approaches.

A RealClearPolitics average of polls shows Sinema with a narrow 1.8 percentage point lead heading into the final month of campaigning.

Democrats see the seat as one they can flip as they face a difficult map in their attempt to take back the upper chamber.

The Cook Political Report, a nonpartisan election forecaster, rates the Senate race in Arizona as a "toss-up."