The 2020 Senate Race in Maine will be the state's most expensive ever, but it will be a small price to pay to rid the senate of Susan Collins. Source: Bangor Daily News House Speaker Sara Gideon, the frontrunner in an upcoming Democratic primary to challenge U.S. Sen. Susan Collins, raised $8.1 million during the pre-primary period, extending her fundraising lead over the incumbent Republican. Updated fundraising reports were due to the federal government on Thursday covering the period from April 1 through June 24.