With just five weeks to the election, Republican Charles D. Baker has pulled even with Governor Deval Patrick in a gubernatorial race shaped by anti-incumbent sentiment and unusually high excitement among Republican voters, according to a new Boston Globe poll. The poll results also suggest that independent Timothy P. Cahill is pulling voters equally from Baker and Patrick, raising questions about the conventional political thinking that his candidacy is undercutting Baker’s chance to defeat the governor in the Nov. 2 election. In the Globe poll, taken last week, Patrick, a Democrat, won support from 35 percent of likely voters, compared...