Good article, Jeff. But I think you miss Brubaker's dilemma. You ask

"Why propose a constitutional amendment unless you are 100 percent confident a majority of the people will vote the way you want them to vote?" Why? Because it does not have to pass for him to gain brownie points from ultra-conservative Lancaster County voters - people he perceives as his base. I believe he was pushed into sponsoring this bill to prove he was worthy of the support of the old guard party leaders like Scott Boyd and Katie True.
I believe Mike when he says he has no negative feelings toward homosexuals. I also think he scared his local party leaders by reaching out to moderate - and even liberal constituents and co-legislators. Mike had a bright future as someone who could appeal to both Republicans and Democrats with an agenda to benefit all of Lancaster County and Pennsylvania. Unfortunatly, he has disappointed us by succumbing to pressure from the hard right.
Don't these guys know movement across the country is away from the social conservatives? People are dropping the Republican party by the thousands because they are tired of social policies of fear and division. True, Lancaster County is a decade behind in politics - but Brubaker just restricted his political career and chained himself to the local party. Once he steps out to a broader constituency, he'll be stepping in the mess he just made by sponsoring this bill.

What changed with Brubaker in just a few months? Read this Hawkes column from January 17: "A senator recounts his freshman year" http://articles.lancasteronline.com/local/4/215227
It says "If Republican voters wanted a firebrand, they could have nominated Heidi Wheaton, Brubaker's opponent in the primary."
Or, maybe they could just break him of his desire for positive change...?

"He said all he's doing is making it possible for the voters to decide if they want gay marriage."
Gee, who could be against that? Unless they knew there was no hope of changing the State Constitution, with votes. Better to use the judiciary to craft such perturbations. Working beautifully elsewhere.