Selzer & Company, an Iowa-based firm, did some polling of “likely Republican caucus-goers” and the results are pretty bad for Jeb Bush. Iowa Republicans gave Mitt Romney better numbers across the board, from being a strong candidate against Hillary Clinton, to understanding their problems, to creating jobs, to combating terrorism. Romney’s biggest advantage (49%-22%) was in “having a vision for the future.”

I think that last result is a pretty strong indication that voters see Jeb primarily as a Bush, and therefore as something past tense. In this kind of poll, you always have to consider the role of name recognition, but that’s complicated by everyone’s familiarity with the Bush family. So, in this case, a lack of familiarity with Jeb specifically means that’s he’s carrying the burden of people’s opinions of his brother and, to a lesser degree, his father.

It’s not that people will change their opinions of Jeb simply by getting to know him better. They’ll change their opinions to the degree that he defies their preconceived notions about him and differentiates himself. If his vision for the future is significantly different from what was on offer during his brother’s presidency, then his poll numbers will move in one direction or the other.

What’s clear from the polling data, though, is that being a Bush is not a plus among Iowa’s Republican base. It’s an anvil around Jeb’s neck.

If we’re talking about just the Iowa caucuses, Jeb has one notable disadvantage over his brother. He’s Catholic, but 56% of the electorate in 2012 was white evangelical. George W.’s conversion was much better suited to winning Iowa than Jeb’s.

Nonetheless, acting super-religious can somewhat compensate for having the wrong religion, as Rick Santorum understood and exploited to win the Iowa caucuses in 2012. The Jeb team is prepared:

A memo from a top adviser to Jeb Bush gives a clue as to how he could connect with the conservative base of his party if he runs for president: talking about his religious faith.

Faith is listed as one of nine “issues you care about” in a memo to Mr. Bush’s supporters from Sally Bradshaw that quotes Mr. Bush on each topic, offering an on-message preview of his potential bid for the Republican nomination.

Referring to his conversion to Catholicism, Mr. Bush says, “My faith was strengthened when I converted to my wife’s faith…It gives me a serenity that, in a world of a lot of turbulence, is really important. It creates a moral architecture that simplifies things. There are views that I have, that are grounded in faith, that really aren’t negotiable and it just simplifies things.”

That memo listing the things that Jeb “cares about” reminds me of his father accidentally reading “message: I care” off a teleprompter during the 1992 New Hampshire primary contest.

In any case, a Catholic (or even a Mormon) can win the Republican caucuses in Iowa, but it’s easier for a Protestant to do so, and the more evangelical the better. This might be even more true in South Carolina where 64% of the 2012 Republican primary voters were white evangelicals.

There’s some national polling from Fox News that suggests that Jeb will be the main beneficiary of Romney’s decision not to run, but national polling doesn’t matter much since very few voters will ever cast a meaningful vote in the Republican caucuses and primaries.

The transfer of support from Romney to Bush may happen organically, but it won’t be due to anything Mitt Romney has done. He’s made clear through selected leaks that he doesn’t think much of Jeb, and in his announcement that he wouldn’t run he said that he hoped and expected that the eventual nominee would be relatively unknown at this point, meaning that it wouldn’t be Jeb among others.