I believe that Hillary's expressions of her Christianity will grow in direct proportion to Romney's assent. She will attempt to exploit latent discomfort with Mormonism by peppering more and more of her rhetoric with religious and theological references subtly and cleverly intended to juxtapose with Mormon beliefs (the centrality and inerrancy of the Bible, Monotheism, etc). Her team will never overtly raise the issue. This will be a classic whisper campaign, aimed primarily at peeling away Red state Bible-belters. Publicly, of course, she'll bitterly deny any such crass sort of political calculation.
Against a backdrop of open-minded sounding platitudes about America's traditions of religious freedom, Hillary will praise Mitt for his family, his choices, his values and so on, carefully avoiding of criticism of Mormonism. But between the lines her message to those Christians who are uncomfortable with Mormonism will be, "Whatever our political differences, at least I'm on your team and not one of those, well, you know ... Nudge, nudge, say no more."
The obligatory "I know everyone knew what was meant but I can't help myself anyway spelling correction": Hillary's expressions of her Christianity will grow in direct proportion to Romney's assent ascent.