Kelli Ward, who is running for Senate in 2018, is urging GOP Sen. John McCain John Sidney McCainMomentum growing among Republicans for Supreme Court vote before Election Day McConnell urges GOP senators to 'keep your powder dry' on Supreme Court vacancy McSally says current Senate should vote on Trump nominee MORE (R-Ariz.) to resign after being diagnosed with brain cancer and pitching herself as a replacement.

"I hope that Sen. McCain is going to look long and hard at this, that his family and his advisers are going to look at this, and they're going to advise him to step away as quickly as possible," Ward told an Indiana radio station this week.

Ward, who has also offered condolences to McCain, added that "as a Christian, I know there can always be miracles. But the likelihood that John McCain is going to come back to the Senate ... is low."

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Ward, who has aligned herself closely with President Trump, lost in the 2016 Senate GOP primary to McCain and is now running against GOP Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (Ariz.) in 2018.

She said McCain's diagnosis could bring the GOP agenda to a halt, adding that with the 80-year-old senator "out of commission, we don't have 51 votes on the the Republican side."

"We can't have until the 2018 election, waiting around to accomplish the Trump agenda, to secure the border and stop illegal immigration and repeal ObamaCare and fix the economy and fix the Veterans Administration," she said.

Republicans have 52 seats. With McCain's absence, that narrows their majority to 51 GOP senators.

Though Republicans are trying to pass an ObamaCare repeal bill and tax reform with only a simple majority, any other priorities, including immigration or veterans legislation, would require 60 votes and the support of Democrats.

If McCain were to resign — something he has shown no sign of doing — Arizona's governor would need to appoint a replacement until a 2018 special election.

Ward is pitching herself as a potential successor, noting she's already run against McCain and worked in the state legislature.

"Well, you know, I certainly hope so because I have a proven track record in the Arizona state Senate of being extremely effective and of listening to the voice of the people that I represent," she said when asked if her name would be included in any discussions on replacing McCain.

Ward's comments, which were first reported by CNN, come after she previously tried to make McCain's age a factor during their primary fight, saying he's "gotten weak" and calling him a "dinosaur."

McCain was absent from Washington this week, recovering from having a blood clot removed from above his left eye. His office announced on Wednesday night that the Mayo Clinic in Phoenix had found a brain tumor.

But the GOP senator has shown no signs of stepping down, continuing to weigh into policy fights and pledging to return soon.

“Unfortunately for my sparring partners in Congress, I'll be back soon, so stand-by," he tweeted on Thursday.