But Ms. McSally was then appointed to the state’s other seat — the one held by Sen. John McCain until his death in August 2018 — and is running for a full term this year in what is again shaping up to be the Republicans’ toughest hold of the election cycle.
This time, though, Mr. Trump will be on the ballot with the 53-year-old Republican, and Ms. McSally is already adopting a Trump-like approach to campaigning after a terse exchange with a CNN reporter last week went viral.
“You’re a liberal hack, buddy,” the senator told Manu Raju, a senior congressional correspondent for CNN, as she refused to answer his questions about the impeachment process.
Fellow reporters rallied to the defense of Mr. Raju, a well-liked member of the press corps, complaining that it was unfair to attack him in that way. Critics quickly pointed out that other reporters, particularly from publications deemed to be conservative, have faced similar jeers from some Democrats for years.
Ms. McSally, unperturbed, released video of the encounter and leaned even further into the flap by registering liberalhack.com and offering T-shirts emblazoned with the slam against Mr. Raju for a $35 donation to her campaign.
MoveOn.org, an organization created to oppose the impeachment of President Bill Clinton in the 1990s but which is not a vociferous proponent of impeaching Mr. Trump, said Wednesday that nearly 5,000 of its members responded to a plea to help Mr. Kelly after the CNN scuffle, donating nearly $100,000 to his campaign.
“Voters want accountability and are fired up to elect leaders who will act as a check on this lawless and corrupt president,” said Rahna Epting, MoveOn’s executive director. “We’ll see Sen. McSally at the ballot box this November.”
Reached Wednesday, the McSally campaign didn’t comment on MoveOn’s announcement.
The way things are going, Mr. Kelly may not need the boost.
He released fundraising numbers showing he collected more than $20 million for his campaign last year and had $13.6 million in the bank. That outdistanced Ms. McSally’s $12 million raised and $7.6 million on hand.
For her 2018 campaign, Ms. McSally raised $21.6 million, close to the $22.2 million raised by then-Rep. Kyrsten Sinema, the Democrat who won the seat vacated by Republican Jeff Flake.
Mike Noble, chief researcher at OH Predictive Insights, an Arizona-based polling firm, said Ms. McSally lost the 2018 race in the outer suburbs of Phoenix.
Dozens of precincts in Maricopa County that voted for Mr. Trump in 2016 voted for Ms. Sinema two years later, and 118 precincts statewide went for Mr. Trump and then for Ms. Sinema.
Ms. McSally flipped only two Clinton-won precincts, both in Pima County.
“If you were to ask me where is it McSally needs to focus and do better — Maricopa County. It’s pretty straightforward,” Mr. Noble said.
In that last race, it was health care that dented Ms. McSally. Her vote for the repeal of Obamacare and her zeal for it — “Let’s get this [expletive] thing done,” she told her Republican colleagues ahead of the vote — hurt her with too many voters.
Mr. Noble said he could see that play out in a couple of areas of Maricopa County that are home to major seniors communities that often vote Republican but rebelled against Ms. McSally.
“She was bleeding from that,” he said.
The Obamacare issue dinged Republicans nationwide.
So far this year, the issue has been less prominent for a number of reasons.
Mr. Kelly, whose campaign didn’t respond to messages from The Washington Times, is running on a standard Democratic message and a unique personal story.
His NASA experience is front and center in his campaign, as is his wife, former Rep. Gabby Giffords, a Democrat whose career in Congress was ended by a gunman who opened fire on her outdoor town hall in a Tucson parking lot in 2011. She retired and became a gun control activist.
Her favorability rating was slightly underwater, at 46% favorable and 47% unfavorable. Mr. Kelly showed at 46% favorable and 27% unfavorable. It’s not that voters don’t know him, but 20% said they had no opinion.
“McSally is incredibly defined. Not a ton of room to go, and she’s pretty much split,” Mr. Noble said. “He’s defined as more favorable as compared to unfavorable. However, he hasn’t really been attacked yet.”
Impeachment, the issue on which the CNN reporter was prodding Ms. McSally, looms large in the race at this point. The senator is a staunch defender of the president, while Ms. Sinema is viewed as one of three Democrats who might break with her party and vote to acquit Mr. Trump.
That could give Ms. McSally cover.
Mr. Trump, who won Arizona by 3.5 percentage points in 2016, led potential Democratic opponents in Mr. Noble’s December polling, though a matchup with former Vice President Joseph R. Biden was close.
With Ms. McSally trailing Mr. Kelly in the same survey, that means some Trump-Kelly voters are out there. If they follow through on Election Day, Arizona could be looking at two Democratic senators for the first time since 1953, when Barry Goldwater won a seat.
“The Republicans got caught flat-footed last election cycle,” Mr. Noble said. “This one will be an absolute barnburner.”