in a solid blue state she has only 49% approval and 41% disapproval. +8 net favorability in a state that leans strongly in your direction isnt a good sign.
https://morningconsult.com/senator-rankings-q2-19-2/

to contrast...the *republican* governor who just won re-election has 73%(!) approval to only 14% disapproval. hes the most popular governor of his state in the nation.
https://morningconsult.com/senator-rankings-q2-19-2/

a solid majority (58%) of people in warrens state didnt want her to run for president.
https://www.bostonglobe.com/metro/2018/09/20/elizabeth-warren-for-president-new-survey-shows-mass-voters-don-love-that-idea/eRMzdOVBxe2Bc0Jxk1v9nK/story.html

so ma isnt quite the liberal/progressive bastion that a lot of people think it is.

the dynamics are there for a moderate repub senate candidate to succeed...especially in a less predictable special/off-year election.