President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE endorsed Sen. 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’s (R-Ariz.) 2020 Senate campaign as she faces a stiff Democratic effort to flip her seat.

“A brave former fighter jet pilot and warrior, Senator Martha McSally of Arizona has done an outstanding job in D.C., and is fully supportive of our agenda – she is with us all the way,” Trump tweeted.

....Martha is strong on Crime and Borders, the 2nd Amendment, and loves our Military and Vets. She has my Complete and Total Endorsement! — Donald J. Trump (@realDonaldTrump) June 25, 2019

McSally ran in 2018 to replace the 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.) but fell short to Democrat Kyrsten Sinema. She was later appointed to her current seat in December after the late Sen. John McCain John Sidney McCainAnalysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE’s (R) death in August, with former Sen. Jon Kyl (R-Ariz.) serving in the interim months.

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McSally is facing off against astronaut Mark Kelly to fill the remaining two years of McCain’s term in what is set to be a tight race. A May poll found the two candidates statistically tied.

The Arizona Republican was out-fundraised in the first quarter of the year, hauling in $2.1 million compared with the $4 million Kelly garnered in his first weeks as a candidate.

McSally tied herself closely to the president in her failed 2018 campaign and has continued to back the White House during her time in the Senate, providing the administration with a key border state ally on its immigration policies.

The Arizona Democratic Party slammed McSally Tuesday as a "rubber stamp" for Trump's agenda.

"Partisanship and party loyalty have always been more important to Martha McSally than putting Arizonans first in Washington. McSally is a rubber stamp for national Republicans' agenda, whether on tax giveaways for big corporations, or the GOP lawsuit to end coverage protections for 2.8 million Arizonans with pre-existing conditions," Brad Bainum, a spokesperson for the Arizona Democratic Party, said in a statement to The Hill.