Jacobs, a four-term Republican from Harford County, has scheduled a news conference at JADs Caddyshack in Essex on Thursday. Sources familiar with the campaign say she will announce her intentions to run for the 2nd Congressional District seat at that time.
Jacobs formed an exploratory committee to look at the race less than a month ago.
The place of the announcement is also significant since it is in Ruppersberger's home county where he served two terms as county executive and two more on the Baltimore County Council. Ruppersberger, a Democrat, was first elected to Congress in 2002.
In recent months, Jacobs, who represents Harford and Cecil counties, has befriended the owners of JADs Caddyshack, sources familiar with the campaign said.
Jacobs would join Larry Smith, a Timonium resident and staffer for Republican Rep. Andy Harris, in the Republican primary. She would not have to give up her seat in the state Senate unless she defeated Ruppersberger.