By ALISA WIERSEMA, ABC News

(WASHINGTON) — In the span of just few months, Sen. Rob Portman of Ohio went from openly discussing his plans to help Republicans defend the 2022 Senate map, to announcing he would not seek reelection and instead plans to retire at the end of his term.

While the news shocked his Republican colleagues on Capitol Hill, the announcement also signaled the starting point of another competitive campaign cycle.

Portman is the third Republican senator from a key swing state to announce his retirement — Sens. Pat Toomey of Pennsylvania and Richard Burr of North Carolina also do not plan to seek reelection in November 2022, making Republicans vulnerable to widening their minority margin in the Senate. GOP concerns over defending competitive seats are further exacerbated by a lack of public commitments from Sens. Chuck Grassley and Ron Johnson to run for reelection in Iowa and Wisconsin.

“Normally the first midterm election after the presidential is good for the opposite party,” Portman said in a November interview with Politico. “Donald Trump just won Ohio by eight points twice. I beat (Trump) by 13 points last time (in 2016). Should be a good year for Republicans.”

Although Portman’s optimism about running for a third term seems to have soured — he cited the “increasingly polarized” nature of politics as his decision not to run on Monday — his earlier assessment of 2022 indicates a favorable playing field for Republicans. In the hours following Portman’s announcement, some of Ohio’s prominent GOP leaders began fielding questions about their professional intentions.

Speculation immediately swirled around the prospects of former President Donald Trump’s longtime congressional ally, Rep. Jim Jordan. He rose to national prominence as a key voice in the House Freedom Caucus and was recently awarded the Presidential Medal of Freedom by Trump. One of the accomplishments listed by the White House at the time of the award ceremony was Jordan having “led the effort to confront the impeachment witch hunt,” a role the sitting congressman has indicated he’s willing to reprise amid the second round of impeachment proceedings against the former president.

During an interview on the conservative media channel Newsmax following Portman’s announcement, Jordan made his allegiance to Trump clear, although he demurred when asked if he would seek a 2022 Senate run.

“I mean we’ll see, I’m focused on my work in the Judiciary Committee,” he said, adding that he is also focused on “doing everything we can to get this thing over with and making sure the president is not convicted in the United States Senate.”

Jordan’s close ties to Trump would likely become a crucial part of his campaign platform if he decides to run.

Trump has already indicated he plans to wade into 2022 contests by backing his former White House press secretary, Sarah Huckabee Sanders, in the Arkansas gubernatorial race. The success of Trump’s endorsements on a national scale would test the longevity of his influence within the party.

“I wouldn’t be surprised to see that Trump would double down on his support for Jordan when it comes to the primaries, which of course are more than a year from now,” said Dr. Paul Beck, professor emeritus of political science at Ohio State University.

Beck said that while he would be surprised if Jordan did not ultimately choose to run, Trump’s likely endorsement may not be enough to solidify the current congressman as a definite front-runner.

“(Rep. Jordan) is somebody who would rally Democrats and independents against him — and some Republicans against him. I think some of the John Kasich people would not at all support (Jordan),” Beck said, referring to Ohio’s former governor, who enjoyed Republican support as a centrist before running for president in 2016.

Ohio voters could see another familiar face in the campaign scramble, as former Rep. Jim Renacci appears to be mulling over his political future. A day after Portman’s announcement, Renacci issued a statement outlining his plans to explore his “options to reenter public office over the next 60 days.”

The former congressman told ABC News that he held a virtual meeting with several state leaders Monday evening and plans to continue holding virtual town halls. Renacci said he aims to start some face-to-face discussions when that becomes possible.

Renacci’s recent statement laid out his imminent plans to speak with voters across the state during a months-long “exploratory deep-dive phase.” Although the former congressman is no stranger to competitive races, he hasn’t been victorious statewide. In 2018, Renacci lost a Senate bid to the state’s current senator, Democrat Sherrod Brown by nearly 7 points.

Brown’s success in winning contests in Republican-leaning territory made him somewhat of a political unicorn that other Democratic Senate hopefuls could try to emulate in 2022. At the time of his victory against Renacci, Brown earned more votes and won by a greater margin than Republican Mike DeWine, who won the 2018 gubernatorial race by 3.7 points. Meanwhile, Trump’s winning margin in the Buckeye State leveled at 8.1 points in both 2016 and 2020.

Rep. Tim Ryan, a top House Democrat and former 2020 presidential candidate, already indicated a willingness to make the leap. Although Ryan’s presidential bid never took off amid the crowded field of candidates, he pitched himself as someone who could win back Americans who had pivoted away from Democrats in 2016 in favor of Trump.

“I’m overwhelmed by supporters who are reaching out to encourage me to run for Senate. I haven’t made a decision yet but I’m looking seriously at it. Ohio deserves leaders who fight for working people,” Ryan tweeted on Monday, hours after Portman’s press conference.

According to Dr. Paul Beck, Ryan would be “a natural candidate for the Democrats” if he won the party’s nomination. In addition to already having a built-in public profile, Beck predicted the upcoming redistricting process would make a Senate bid more appealing for the congressman who is now serving his 10th term in office.

“We will have redistricted House districts in 2022. My guess is that Ryan will run in a district — if he seeks reelection — that is less favorable to him. The district he currently occupies has been sort of trending away from the Democrats,” Beck said.

Dayton Mayor Nan Whaley also indicated interest in running for Portman’s seat. In a Monday tweet, Whaley thanked supporters for “all the encouraging words” and warned of a competitive election cycle in 2022.

“While I’m still deciding what I will do next, I hope you’ll support us as we do everything we can do to support Democrats in 2022,” she said.

Although Biden flipped Dayton’s Montgomery County in November, Buckeye Democrats have generally had a rough track record over the course of the last decade. The state is currently led by a Republican governor and the GOP controls both chambers of the state house. In Washington, the Ohio delegation includes three times as many Republicans as Democrats. As implied by Whaley, the competing opening for Democrats to run a candidate against incumbent Gov. Mike DeWine would further raise the stakes in 2022.

“What the Democrats don’t have is a lot of bench strength — they don’t have anybody with a clear, statewide visibility that would have probably a major edge in the primaries, and so that’s what is going to be as exciting as the Republican side will be,” Beck predicted.

Copyright © 2021, ABC Audio. All rights reserved.