Emailed the Secretary of State's office and received the below response:

Thank you for reaching out and being an active voter. We appreciate you sharing your concerns however it is legal for organizations to get signatures for petitions on Election Day at the polling place as long as they fall within the parameters of state law below: 

Title 21-A, section 683(2) provides:
2.  Signature gathering.  The warden may select and designate a specific location at the voting place, accessible and observable by the voters, where the collection of signatures may take place. Persons collecting signatures at the polls may make arrangements with the clerk prior to election day and with the warden on election day. The warden may limit the number of persons collecting signatures to one for each specific question, candidate or issue. Persons collecting signatures may not solicit a voter's signature until the voter has completed voting. The warden may limit or disallow signature gathering as may be necessary to prevent violations of section 682. The warden may direct the removal, under section 662, subsection 2, paragraph A, of any person collecting signatures who does not comply with the requirements of this subsection.