PHOENIX — Rep. Martha McSally is planning to enter Arizona's 2018 Senate race, giving Kelli Ward new competition in the GOP primary.

The lawmaker has told her Republican colleagues in Arizona's delegation that she intends to enter the Senate race but didn't indicate when she would formally announce her bid, according to two people with knowledge of the conversations.

Her decision will further shake up the state's political landscape. Sen. Jeff Flake announced two weeks ago he was abandoning his re-election bid amid sinking polling and high-profile clashes with President Trump.

McSally would be the first high-profile name to join the Senate race since Flake's retirement announcement. Jay Heiler, a longtime lobbyist and member of the state's Board of Regents, has formed an exploratory committee. Others, including former members of Congress Matt Salmon and John Shadegg, have weighed a Senate bid but have taken a pass, at least for now.

McSally has been especially tight-lipped about the races, but seemed to telegraph a Senate run last week in her campaign's response to an attack from a PAC supporting Ward.

In the response McSally echoed Trump's familiar charge of "fake news" and embraced an assessment of her record as Arizona's most reliable vote for the Trump administration. McSally has avoided commenting on Trump's many controversies throughout the 2016 presidential campaign and since Trump has taken office.

But McSally can expect opposition from some on the right, including a political action committee aligned with the conservative Club for Growth, which warned recently that it would oppose her candidacy.

Read more:

Senate poll: GOP voters uncertain who they want to replace Jeff Flake

Rep. Martha McSally tries to block out the chaos in competitive Arizona district

McSally, who represents the Tucson-based 2nd District, was already facing a difficult re-election campaign to the House.

Last year she breezed to a second term in the evenly divided district, but she's faced anger from many there for supporting the Trump agenda, especially since voting in May for the failed GOP-led health care overhaul.

McSally trailed in some polls and faced formidable Democratic opposition led by former congresswoman Ann Kirkpatrick, an adept fundraiser who has consolidated her party's establishment support and the money that goes with it.

So far, McSally's voting record has made her the most supportive of the Trump agenda among Arizona's House members, as tracked by the website FiveThirtyEight. That has been a mill stone in her divided district but could be an asset in securing the GOP nomination in a statewide Senate race.

McSally will likely lean heavily on her military background as the first woman to fly a combat mission for the Air Force. She is a prolific fundraiser and seen as a steady hand who could expect significant support from a wider network of party donors.

By contrast, Ward, a former state senator, has struggled to raise money this year even as she surged in the polls and pulled in a supportive tweet from Trump in August.

McSally's plan creates a vacuum for Republicans in her district and will give new confidence to Democrats, who will instantly view her House seat as key to winning the net 24 seats needed to retake the House majority.

Her move also adds another woman to a Senate race that already has at least three female contenders. In addition to Ward, Rep. Kyrsten Sinema is vying for the Democratic nomination against political newcomer Deedra Abboud.