Rep. Ruben Gallego will not run for the U.S. Senate in 2020’s special election, he told The Arizona Republic on Monday, clearing the path for retired astronaut Mark Kelly to take on incumbent Republican Sen. Martha McSally without a potentially bruising primary fight.

Gallego’s decision will disappoint progressive Democrats, who represent the left flank of the party and are especially hostile toward President Donald Trump.

Those voters wanted Gallego, 39, to wage a fight against Kelly, who is presenting himself as a centrist Democratic candidate who will make decisions based on data and science, not partisan politics or ideology.

By removing himself from running, Gallego, D-Ariz., also dashes GOP hopes of a competitive Democratic primary race that could have freed McSally, R-Ariz., to focus on her own campaign message while Gallego and Kelly battled it out for their party's nomination.

In Gallego, Republicans saw an opportunity to wound Kelly by forcing him to answer for the more liberal positions that reflect the party's general direction.

“I don’t want to engage in a bitter primary all the way until the general election, and then turn around and try to run, whether it’s me or Kelly, against McSally in a year when the Democrats need to win the Senate seat and take the state,” Gallego told The Republic. “It’s just not in the best interest of the state or the Democratic Party to be engaging in that. … If Republicans are excited to see a spirited and nasty primary, they’re going to have to look somewhere else because I’m not going to take part in that.”

Gallego, a three-term congressman and former Marine Corps combat veteran of the Iraq War, had been laying the foundation for a potential run up until last weekend.

In recent weeks, he was meeting with potential donors and supporters here and across the nation. He was telling associates, friends and Democratic players in Phoenix and Washington, D.C., that he was gearing up for a potential run.

In the end, he decided to run for re-election in the 7th Congressional District, a Democratic stronghold where he is widely seen as safe.

Gallego said he will spend this cycle getting out the vote and helping Democrats build on Democrat’s 2018 performance, when the party won two statewide races, capped by Kyrsten Sinema’s historic Senate victory.

The 2020 election will fill the final two years of the late Sen. John McCain’s unexpired term. The winner would again face voters in 2022 to serve the full six-year term.

Gallego said he did not inform Kelly of his decision Monday, but planned on talking with him this week.

"As a Navy guy, I know it's always better to avoid a fight with a Marine," Kelly said in a written statement to The Republic. "I have a lot of respect for Congressman Gallego’s service to our nation. I look forward to working with him to stand up for Arizona families."

Arizona set to be battleground state

Arizona is poised to be a battleground state next year and is expected to be among a handful of states that could swing the presidential election.

Trump carried Arizona over his Democratic challenger Hillary Clinton in 2016 by fewer than 4 percentage points, and last year’s competitive Senate election will ensure both parties and their candidates will be investing time and money in 2020.

With Gallego out, the 2020 race so far pits against each other two combat pilots who grew up on the East Coast and relocated to Tucson.

McSally, 53, was an Air Force colonel. Kelly, 55, was a Navy captain before becoming a NASA Space Shuttle pilot.

Voters are familiar with Kelly’s space days and his marriage to former Democratic Rep. Gabrielle Giffords and his gun-control activism that followed the 2011 assassination attempt on her.

But they know little about his policy positions beyond the broad themes that he has touched on in his announcement video and public events.

Already, outside Republican groups are seizing on his past speaking engagements to suggest he is cozy with the very corporate interests that he has pledged to distance himself from in the form of political action committees.

Since launching his campaign, Kelly has raised more than $3 million from more than 45,000 contributions.

McSally is not expected to draw a competitive primary challenger, but she enters the race under pressure to demonstrate that she can reach beyond the base GOP voters to moderates and independents whose support she did not have last year.

She lost her 2018 Senate race but the governor appointed her to the seat once held by McCain.

Since taking office in January, McSally has stuck with Trump on the most consequential decisions. Earlier this month, she voted against a Democrat-led measure to terminate the president’s declaration of an emergency along the Mexican border.

In a rare break with Trump, McSally defended McCain after the president spent days issuing blistering attacks on the late senator who died last August following a battle with brain cancer.

McSally said she told the president that McCain and his family deserve respect.

Have news about Arizona's U.S. senators or national politics to share? Reach the reporter on Twitter and Facebook. Contact her at yvonne.wingett@arizonarepublic.com and 602-444-4712.

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