Comparing last week’s election to the January special election for US Senate provides an interesting look at how Scott Brown was successful while Charlie Baker came up short. Baker’s loss was essentially a carbon copy of Brown’s victory when looking at men, Democrats, and Republicans; women and unenrolled voters broke more toward Gov. Deval Patrick and thereby changed the outcome.

To compare the two races, I looked at a Washington Post poll conducted in Massachusetts in the immediate aftermath of the January special election, and compared those results to the MassINC Polling Group Post Election Poll, conducted last week.

Men went for Brown by 14 points and Baker by 13 points, essentially the same margin. It was among women where the gubernatorial election differed strongly with the January special election. In January, Brown closed the typical gender gap among female voters, losing to Martha Coakley by just 3 points. In November, however, Patrick ran up a 24-point margin among women, which partially explains the difference in the outcomes.

A similar trend shows up when looking at party affiliation. Looking first at Democrats, the margin for Coakley was 64 points, while for Patrick it was 65. The margin among Republicans was also similar—Baker locked up Republicans, winning an 83 point margin to Brown’s 90 points. While this 7-point difference may seem noteworthy, Republicans make up only 12 or 13 percent of the electorate in each cycle, meaning a 7 point difference in the margin among Republicans is only about 1 percent of the overall electorate.

It was among unenrolled voters where the real change occurred. While Brown won unenrolled voters by 31 points, Baker’s margin was only 14. In a state where just over half the electorate is unenrolled, a Republican candidate needs a very large margin, such as Brown accumulated, in order to be successful.

To be successful and get reelected, Brown will need to maintain his popularity among the two groups who went for him in January but did not go for Baker. He is off to a good start with this task. Two thirds of unenrolled voters and 48 percent of women view him favorably, according to Suffolk’s final pre-election poll. These levels are nearly identical to the percentages of the vote he received among each group in January. His task is to maintain these levels of support even as he becomes, in his own words, the Democrats’ “biggest target.”

Steve Koczela is the President of The MassINC Polling Group, where he has grown the organization from its infancy to a nationally known and respected polling provider. During the 2014 election cycle, MPG conducted...