Why did the Left go to the Wedge Strategy in 2012?

The answer may be in the numbers.

According to this article on Spero Forums:

Support for Obama slips as Catholics plan weeks of protest

The US Conference of Catholic Bishops is calling for two weeks of protest in June and July against Obamacare and its encroachment on religious freedoms.

President Obama has seen his standing among Catholic voters, a crucial segment of the electorate, slip in recent weeks, and a looming confrontation with Catholic activists could make it worse. Democrats want voters this year to focus on what they have branded a war on women, but the flip side of the debate—the so-called war on religion—is not going away anytime soon.

This could be the telling fact:

Obama has lost support among Catholic voters since the beginning of his term. A March 21 poll by the Pew Research Center found a “noticeable shift in opinions” among white Catholics in their views of the administration. Thirty-one percent of white Catholics now describe it as unfriendly to religion, compared to 17 percent in August of 2009.

Given Obama's leftists intellectual culture, it is entirely possible that he and his inner circle figure that this shift represents the reactionary work of the Catholic bishops, and therefore in a classic Leninist move, the counter-strategy is to isolate that leadership from the "Catholic proletariat."