Margaret Carlson and Ramesh Ponnuru are discussing Republican politics and policy.

Margaret: Until Jeb Bush's new book and his round of muddled interviews, I had vowed not to talk about 2016. People rightly hate us for writing about the next election while they’re still counting votes from the last.

But I'm so taken with poor Jeb and his brother problem. First it was his blood brother, George W. George wasn't supposed to run for president -- Jeb was. When the 2000 presidential election came down to a troubled recount and Governor Jeb Bush of Florida had to drag Governor George Bush of Texas across the finish line, the Bush family saga looked Shakespearean. He couldn’t recuse himself "of being my brother's brother," he said.

To continue the drama, Jeb now has to contend with his political brother -- Senator Marco Rubio, the brightest star in the Florida Republican firmament. Bush has mentored Rubio like a brother and has described him as "the real deal." So it was news this week when Bush moved to the right of his brother-in-arms on immigration, changing his position on a path to citizenship for undocumented workers in the U.S.

If Bush decides to run, the real deal would now be his main competitor for the presidency. It's good Bush has such a sunny disposition. Rubio has ascended while Bush was sitting on the sidelines, hoping the public would get over his brother's legacy of two wars and huge deficits. If they’re both candidates, Rubio and Bush will divide the world of rich donors in Florida and nationally. Some Republicans who begged Jeb to run last year have found a new love.

Ramesh, you are pushing conservatives to come up with both better policy and better politics. Now the immigration issue, something you may have been getting traction on, is confused.

Maybe Bush was hurt by the long lead time publishers still observe: As he was turning in his manuscript last fall, Bush couldn't have known how far and how fast his party would move on immigration after their whomping in the 2012 election. Bush is also a little rusty, having been out of the scrum since the dawn of hyperpartisan and social media.

What is surprising -- or maybe it's just the Newt Gingrich School of Book Promotion, in which mulling a presidential campaign is a sales tactic -- is how un-coy Bush is being about running. I think he's sending a message: He doesn't want to be outpaced by a younger sibling again.

(Margaret Carlson is a Bloomberg View columnist. Follow her on Twitter.)

Ramesh: Like you, Margaret, I have the strong sense that Jeb Bush wants to be president. I think he should have been a candidate last time. I understand why he wasn't. He must have thought it was too soon after his brother’s presidency ended, especially since it ended badly, and he didn’t want to run against an incumbent.

All of that is true, but it should have been outweighed by what was in the “pro” column: Winning the nomination would have been much easier in 2012 than it will be in 2016.

Unlike any of Mitt Romney’s other rivals, Bush would have been competitive with Romney among both conservatives and the party establishment and had his own national fundraising base. The stop-Romney faction would have had somewhere credible to go.

If Bush runs in 2016, he will be up against a group of Republicans who weren’t ready in 2012 but who excite the party. And as you suggest, there might not be room in the field for both Bush and Rubio. If I had to bet -- and I don’t, but I will anyway -- I’d guess that Rubio runs and Bush doesn’t.

Until they each make their decisions, and probably even afterward, attention will be drawn magnetically to even tiny policy differences between them.

On immigration, I don’t think that Bush has executed much of a flip-flop or even gotten much to Rubio’s right. As I understand it, he wants illegal immigrants who came here as adults and decide to stay in the U.S. to be given legal-resident status but not citizenship, and he wants those who want citizenship to go back to their home countries and get in line. (And as hard as it is for me to imagine both Bush and Rubio running, it is even harder to see Bush’s being psychologically prepared to run to Rubio’s right on immigration.)

I think you are right, on the other hand, to suggest that what Bush is doing makes no political sense. He has sought to get Republicans to move on immigration in large part because they need to get more support from Hispanics. But how attractive is a Republican message of “Come here and work but don’t think about becoming a citizen” going to be to Hispanics, compared to what the Democrats will be able to offer?

Even if Bush’s idea became law (which it won’t), Democrats would immediately start campaigning for liberalization and Republicans would be struggling to explain that they’re not anti-Hispanic. Republican proposals for temporary work programs suffer from the same flaw.

So what do you make of the other possible 2016 Republican aspirant who has been in the news this week, Margaret? Senator Rand Paul kept up a spirited filibuster of John Brennan’s nomination to head the CIA. I am not a fan of the administration’s approach to drone strikes, but I could have done without Paul’s references to Hitler, martial law and internment camps. But there hasn’t been much civil libertarianism from elected Democrats during this administration, so I guess those of us who worry about these things have to take what we can get.

(Ramesh Ponnuru is a Bloomberg View columnist. Follow him on Twitter.)

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