WASHINGTON ― Democratic operatives are ecstatic about Mark Kelly’s decision to run against appointed Arizona Republican Sen. Martha McSally in 2020. He’s a dream candidate: a naval aviator-turned-astronaut who’s made four trips to space, the husband of a Democratic Party star who survived an assassination attempt, a gun control advocate who’s helped a nationwide network of candidates and built a matching network of donors. However, the party’s left wing is holding off on the celebrations for now. Public records show Kelly voted in the 2012 GOP primary while living in Texas, meaning he likely cast a ballot for either Mitt Romney or one of the host of conservatives running against President Barack Obama and either Ted Cruz or David Dewhurst for Senate. (A Kelly spokesperson said he voted for Obama in the general election.)

Joe Raedle via Getty Images Mark Kelly, a gun control advocate, former astronaut and husband of former Rep. Gabrielle Giffords, will be a top Democratic contender for Arizona's Senate seat.

And progressives both in the state and nationally have long been preparing for Rep. Ruben Gallego, a Latino veteran of the war in Afghanistan and member of the Congressional Progressive Caucus, to run for the seat. Gallego is still considering a bid, potentially creating an ideological clash with Kelly. It’s one of a host of potentially pugnacious primaries Democrats could face in 2020 as they seek to win back control of Congress’ upper chamber. “I’ve made no secret of the fact that I’m looking seriously at running for the U.S. Senate in 2020, and that hasn’t changed,” Gallego wrote on Twitter Tuesday, the day Kelly announced his campaign. “I’ll be making a final decision and announcement soon.”

I’ve made no secret of the fact that I’m looking seriously at running for the U.S. Senate in 2020, and that hasn’t changed. I’ll be making a final decision and announcement soon. #AZSEN — Ruben Gallego (@RubenGallego) February 12, 2019

A Democratic source said Gallego’s chief of staff, David Montes, a veteran of former Senate Democratic leader Harry Reid’s office, has been taking meetings with media consultants and pollsters in recent weeks to prepare for a potential bid. Gallego isn’t 100 percent certain to run; his team is still investigating whether it could raise the cash necessary to challenge Kelly in a primary. McSally, a moderate-turned-Trump ally who narrowly lost the U.S. Senate race to Democrat Kyrsten Sinema in November and was appointed to the seat formerly held by the late John McCain in December, is considered one of the most vulnerable Republicans on the ballot in 2020. A primary battle between Gallego, 39, and Kelly, 54, could be one of several such contests Senate Democrats face this cycle. While it’s still early in the recruiting process ― Arizona’s primary won’t be until August 2020 ― there’s also the potential for intraparty clashes to determine who will face incumbent Republicans in Colorado, Georgia, Iowa, Maine and North Carolina. Races in those five GOP-held states, along with the Democrats’ defense of seats in Alabama, Michigan and New Hampshire, are likely to determine which party controls the Senate in 2021. (Democrats are also likely to look at redder territory, including Kansas, Kentucky, Montana and Texas.) In Colorado, a host of Democrats are likely to compete for the right to challenge GOP Sen. Cory Gardner. Two Democrats who have run for statewide office in the past ― former state House Speaker Andrew Romanoff and former state Sen. Mike Johnston ― have already entered the race, and another former state House Speaker, Crisanta Duran, is also considering a challenge to Gardner. In both Georgia and North Carolina, Democrats are focused on wooing candidates who could clear the field: Senate Minority Leader Chuck Schumer (D-N.Y.) and the Democratic Senatorial Campaign Committee’s pursuit of former gubernatorial candidate Stacey Abrams to run against Sen. David Perdue is no secret, and Democrats are eyeing Attorney General Josh Stein in North Carolina as a challenger to Sen. Thom Tillis. But if either candidate opts against the run, the field would be wide open. In Iowa and Maine, no consensus candidate has emerged but operatives believe women would be best to challenge Sens. Joni Ernst and Susan Collins. The Next Mission For An Undefined Candidate

Kelly’s strengths are readily apparent. As the leader of Giffords, the gun control group named for his wife, shooting victim and former Rep. Gabby Giffords (D-Ariz.), he’s become a high-profile advocate on a key issue for the Democratic base and played a major role in raising and spending more than $17 million for candidates across the country last cycle. His introductory video, however, makes little mention of his gun control work, instead focusing on the rest of his biography: The son of a woman who became one of the first female police officers in the 1970s, he joined the Navy, flew combat missions in Operation Desert Storm and become an astronaut alongside his twin brother. He then left NASA to help Giffords with her recovery. The sterling biography, however, hides a candidate who is still ideologically undefined. In the launch video, Kelly makes his opposition to gerrymandering and refusal to take corporate PAC money clear, but how he would solve other problems mentioned in the video ― high health care costs, wage stagnation ― is left unsaid. As one Gallego ally, granted anonymity to speak about Kelly’s weaknesses, said: “We still don’t know a lot about Mark.” Kelly does take a firm stance on his belief in man-made climate change. 314 Action, a group that backs scientists for office, cited that as a reason to quickly endorse him. “Very few people have had the type of view Mark has of the damage climate change has done to our planet,” said Josh Morrow, the group’s executive director, referring to Kelly’s time in outer space. Kelly’s campaign didn’t make him available for an interview, but he told the Arizona Republic he sees himself as someone who’s “independent” and is “not going to look at these issues through a partisan lens.” Sinema, who is now seen as one of the most conservative Democrats in the Senate, used similar rhetoric during her 2018 win over McSally. And his vote in the 2012 GOP primary is easy fodder for a Democratic rival. Kelly’s campaign said the candidate didn’t remember whom he voted for in either the presidential or Senate primaries that year. “Mark was an independent at the time, and because President Obama was uncontested, Mark voted in the Republican primary,” said Jacob Peters, Kelly’s communications director. “He proudly voted for President Obama in the general.” Gallego’s Uphill Battle

ASSOCIATED PRESS Progressives don't have a great record in recent Senate primaries. Rep. Ruben Gallego will try to change that.