ATLANTA — Stacey Abrams said Tuesday that she won't run for the U.S. Senate in 2020 but left open the possibility she could launch a presidential campaign.

The decision not to challenge Republican U.S. Sen. David Perdue follows months of speculation about the Democrat's next political step after her narrow loss in last year's race for governor.

"I've been deeply honored by so many fellow Georgians asking me to serve," she said in an interview. "But my responsibility is not simply to run because the job is available. I need to run because I want to do the job."

It triggers a new phase of the Senate race, which has been slow to develop while Abrams has deliberated. She plans to stay neutral in that contest, which so far has attracted one candidate  who said she would run only if Abrams does not.

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And it opens a new round of scrutiny over whether she will join the growing presidential field, or emerge as a White House hopeful’s running-mate, a possibility that heightened after she delivered her party’s rebuttal to the State of the Union.

If she doesn't make a White House run, Abrams is likely to prepare a 2022 rematch against Gov. Brian Kemp, who bested her by about 55,000 votes in a contest marred by allegations of voter suppression. After 10 days of legal wrangling and vote-counting, Abrams ended her campaign but refused to call it a concession.

>> On AJC.com: In AJC interview, Abrams reveals why she won’t run 

Her profile has only grown after that election as she's traveled across the nation on a book tour. She's hit the late-night talk show circuit, attracted sold-out crowds from Nashville to Seattle and drawn huge audiences to podcast tapings.

Closer to home, she's trekked across Georgia on a "thank-you tour" to reconnect with supporters; appeared on local Super Bowl ads to boost her Fair Fight voting rights group, which is challenging state electoral policies in court; and sharply criticized the anti-abortion "heartbeat" measure backed by Kemp.

While her national image has soared, an Atlanta Journal-Constitution poll showed Abrams' favorability ratings in Georgia have dipped. The poll, released in April, showed about 45% of Georgia voters view her favorably, compared with 52% in January. Her unfavorable rating jumped 5 percentage points to 45%.

>> Click here to watch a video of her announcement

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