Republican Gov. Doug Ducey effectively picked a front-runner in the 2020 special U.S. Senate election Tuesday when he appointed Martha McSally to the seat long held by Arizona political giant John McCain.

The governor's political calculus for the appointment appeared to weigh who could hold the seat in Republican hands for 2020 after a bruising loss for the party in 2018, consultants said.

And that calculus led him to McSally, the Republican candidate who won more than 1 million votes in November, but lost to Democrat Kyrsten Sinema in Arizona Democrats' first Senate win this century.

Some Republicans say McSally represents the party's best bet to win the 2020 special election.

Before the election, her time in the House labeled her a pragmatic problem-solver who was willing to work with the other party to get things done, similar to Sinema.

McSally has stood for election, unlike some of the names being floated as potential picks, Republican consultant Kim Owens said. She was the “obvious choice,” despite her loss in the contentious Senate race, and she sets a path for the GOP to hold the seat come 2020, Owens said.

“You would never put someone in that position who wasn’t capable of winning in 2020 or who wasn’t willing to do the work necessary to win,” Owens said.

READ MORE: How the McCains view the McSally appointment

But Democrats say they have already beat McSally once and can do it again.

Chad Campbell, a Democratic consultant, said the McSally appointment goes against the wishes of the voters, who decided not to elect McSally in November. He especially wondered how independent voters would take the news, given their role in helping Sinema win this year and their expected role in future elections.

He sees Ducey’s choice as risky, especially for the swayable, independent voters who helped elect Sinema. McSally was already rejected once on a statewide ballot; why would voters do differently in 2020?

The appointment makes the 2020 Senate election “very, very competitive,” he said.

“Democrats have already beat McSally once, so pretty sure we can do it twice,” Campbell said.

OPINION: Allhands: Will McSally and Sinema let bygones be bygones?

The donors on the Republican side quickly made clear after Ducey's announcement that they were on board to help McSally win come 2020, though.

Defend Arizona, a political-action committee that spent big to help McSally this year, said in a statement that it "look(s) forward to supporting her in 2020."

Pressure from Washington?

Some saw major influence on Ducey's decision coming from Washington, D.C., where McSally supporters such as Senate Majority Leader Mitch McConnell sought to elevate her.

Reports from national media in recent days and weeks speculated on how McSally fared in Ducey's eyes, with some noting McConnell's efforts to influence Ducey's decision.

READ MORE: Martha McSally appointed to John McCain's Senate seat

She also had the support of Jon Kyl, who was first appointed by Ducey after McCain's death earlier this year but will leave the office by the end of the year. Kyl, one of McSally's mentors, said he couldn't think of "anybody more qualified" for the job.

In a joint press conference with McSally on Tuesday, Ducey said he read "with great interest" reports out of D.C. about his thinking and how it aligned with Republican leaders.

"But there was one source and one name missing, and that was mine," Ducey said. "I think the fact that I'm standing here and now with Martha McSally at my side, making the appointment to the United States Senate, says everything that needs to be said."

READ MORE: Full remarks: Ducey announces McSally as choice for Senate

The question of how voters decided in November also appeared to weigh into Ducey's decision.

"The voters did make their choice, and I believe that the voters had two excellent choices in this past election," Ducey said. "Martha McSally received over 1 million votes to the United States Senate, and now she will be serving alongside senior Sen. Kyrsten Sinema."

At the press conference, McSally repeatedly said she was humbled and grateful for the appointment. She highlighted McCain's service and legacy and promised she would work productively with Sinema, saying the campaign was behind them.

Owens, the GOP consultant, said Ducey's McSally pick fits with his track record as a consistent, disciplined person.

“Surely there were people trying to grease the wheels, so to speak, but at the end of the day, with or without influence, he would have come to the same decision,” Owens said.

READ MORE: Partisan divide emerges after Ducey's appointment of McSally

Campbell said it appeared Ducey’s decision was influenced by national pressure from Republican elected officials like McConnell and funding groups.

But Campbell also said some other qualified potential appointees may not have wanted the job because it would set off an “endless cycle of electioneering” that would be tough to manage. The 2020 special election would likely kick off immediately, followed by a 2022 run for the seat's regular-cycle election.

Democrats: It'll be another close race

No matter the external forces influencing Ducey, some Democrats said Ducey's choice subverted November's results.

And McSally could be a risky choice for Republican prospects in 2020 because she already lost once in a midterm, which typically skews more favorable to Republicans in Arizona.

OPINION: Roberts: McSally gets the Senate job, but can she keep it?

Lisa Fernandez, a Democratic consultant, said she saw Ducey’s choice as “very strategic.” He could have chosen to appoint a placeholder who wouldn’t run in 2020 or position a front-runner, and he chose the latter, she said.

There may have been pressure from Washington, she said, but the motivations were likely the same in Ducey’s mind and in D.C.

Both were focused on finding their best chance at winning the 2020 election and fighting off gains made by Democrats here, she said.

“They want to do whatever they can to stop that,” Fernandez said.

Republic reporters Maria Polletta and Yvonne Wingett Sanchez contributed to this article.

READ MORE: Sinema will be Arizona's senior U.S. senator, Ducey says