But his stance on marriage is what has disquieted people who had counted on Mr. Walker taking a more restrained approach to the culture wars.

For several months, according to four people briefed on the discussions who were not authorized to describe an off-the-record meeting, Republican donors who were advocates for legalizing same-sex marriage had worked quietly to try to build bridges to Mr. Walker, whose wife has a lesbian cousin whose wedding reception Mr. Walker attended…

“Scott takes this path at his peril in New Hampshire,” said Charlie Bass, a former congressman there. By aligning himself with more conservative candidates on marriage, Mr. Walker puts at risk the support of more economy-focused voters in the first primary state, Mr. Bass said…

“He’s an establishment guy trying to show his conservative credentials,” said former Representative Tom Reynolds of New York. “He’s got to go in and win Iowa, and therefore his message has to resonate enough there on the right.”