He helped elect Trump. He knew exactly what he was doing by so publicly blanking his ballot. “They both suck” was a quintessentially pro-Trump talking point designed to keep iffy Democratic/independent voters home. It worked to perfection.
Take a look at the popular vote numbers for the last four elections.
Both parties have received around 59 million votes on their worst days. That’s where both parties wound up this year. Bush may actually have won over some Democratic-leaning voters, because he got 62 million votes. Romney and McCain both got slightly more votes than Trump, and still lost badly. Because in both of his races, Obama turned out voters who stayed home in 2004 and 2016.
Governor Baker’s “they both suck” shtick was all a mind game played by the GOP establishment to depress Democratic turnout. Don’t let him wash his hands of Trump and pretend he was neutral. Maybe some were too dumb to understand it and were sincere in saying both candidates suck. But he’s a smart man. He knew what he was doing. Make him pay the price in 2018.