the Massachusetts GOP is gazing longingly at 1990, the last time that anti-incumbent fever put one of their own — Bill Weld — in the governor’s office. And Charles Baker, favored to win the right to challenge Gov. Deval Patrick and independent Tim Cahill, seems to be emulating Weld’s mix of fiscal conservatism and social liberalism. So where would Baker need to pull votes away from Patrick? The map below gives some clues. Cities and towns in green were especially supportive of regime changes in both 1990 and 2006. That is, they gave both winning candidates percentages above their statewide showings (50.2 percent for Weld, 55.7 percent for Patrick).

There are towns all over the state in this category, but the real treasure trove of votes is in Boston’s western suburbs. Acton, Concord, Lexington, Needham, and Wellesley all gave more than 55 percent of the vote to both Weld and Patrick. Some other places won by Weld — including Brookline, Newton, and Sharon — have since become more consistently Democratic and aren’t as likely to go GOP in 2010, but Baker will have to cut down on Patrick’s 2006 margins in these communities to win statewide. (A counter strategy involves places that have been cool toward reformers, including Lowell and Quincy. These blue-collar cities helped Paul Cellucci retain the Corner Office for the GOP in 1998 — but they are also a natural base for Cahill.)

Affluent, well-educated towns (which also include Baker’s hometown of Swampscott) trended toward Republican Mitt Romney when he was elected governor in 2002, and they went overwhelmingly for President Barack Obama, a Democrat, in 2008. There’s a pattern of support here for outsiders running against “politics as usual.” The question is whether voters will give Patrick more time to shake things up on Beacon Hill or go with a new face. In 2006, one sign of Patrick’s strength was the number of together we can lawn signs and bumper stickers along Route 2. If you want to know how this year’s election turns out, an apple-picking excursion sometime in late October might be instructive.