Sen. Elizabeth Warren, D-Massachusetts, made an announcement via social media, telling followers: "I'll be making a BIG announcement about my 2020 plans on Sat., February 9," encouraging followers to visit her website for more information.

The exact location of Warren's announcement is set to be unveiled this weekend, aides said.

Warren launched her exploratory committee Dec. 31, saying she would make her bid official at a later date. In the weeks since, she has visited the early primary states as her campaign team continues growing in Iowa, New Hampshire and at her national headquarters in Boston.

The location and staging of formal kickoffs has become an early proxy battle among Democrats who've announced campaigns or are still thinking about it.

Sen. Elizabeth Warren, D-Mass., seen Jan. 12, 2019. Getty

In a campaign so far devoid of reliable polling data for fundraising reports, a campaign's first big event is one measure of early viability and Warren's formal kickoff will surely be measured against her other rivals who've already announced.

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Former Housing and Urban Development Secretary Julián Castro drew about 4,000 people to a weekend rally earlier this month.

Sen. Kamala Harris, D-California, earned considerable buzz among party activists for her kickoff rally last weekend, attended by roughly 20,000 people last weekend in her birthplace of Oakland, California. She also raised more than $1 million in the first 24 hours after her campaign's launch on Martin Luther King Jr. Day, a seven-figure haul not believed to have been matched by any other candidate already in the race or still exploring their viability.