Republican presidential nominee Donald Trump. (Mark Wallheiser/Getty Images)

Donald Trump will give the most important speech of his presidential campaign tonight in Arizona as he tries to clarify his decidedly muddy position on immigration. Looking for some sense of what he might — and should — say, I reached out to Becky Tallent, who is perhaps the leading immigration expert within the GOP. She has served in a variety of roles for Sen. John McCain (Ariz.), including as chief of staff, and in 2013 was hired by then-House Speaker John A. Boehner (Ohio) to oversee the push for immigration reform (which never happened). Tallent is now the head of government relations at Dropbox, but she spoke to me only as a private citizen who knows a heck of a lot about immigration and the GOP. Our conversation, conducted via email and edited only for grammar, is below.

FIX: What do you expect to hear from Donald Trump on immigration Wednesday night? Is it possible for him to find common ground between the views he espoused earlier in this campaign and those put forward by the likes of Jeb Bush and Marco Rubio? If so, how?

Tallent: Only a fool would predict what Mr. Trump is going to say at a rally. However, the message that seems to be coming out of Mr. Trump's camp is border security first, expedited deportation of criminal aliens and building the wall. These are all proposals that were put forward by the Gang of Eight in 2013 and by other presidential candidates this cycle. There is absolutely nothing revolutionary or new here. Obviously the question is what to do with the rest of the unauthorized people that are here. If you want to use the word "pivot" or not, what we appear to have is a candidate facing the realities of a general election and seeming to, we'll call it "evolve," on this point. He clearly wants to appeal to the undecided Republican voters who are desperate to find a reason to vote for him and against Secretary Clinton. However, Trump still can't seem to resist the praise and support of the hard-line immigration voters. I'm not sure even Mr. Trump's advisers truly know what will be said on Wednesday night, but I hope there is a camera on Joe Arpaio for reaction shots throughout.

FIX: You once worked for John McCain. He famously/infamously walked away from comprehensive reform after it nearly sank his 2008 campaign. Two years later he was running ads insisting we needed to “complete the danged fence.” What lessons do you take from McCain’s immigration journey?

Tallent: I would argue that McCain did not pivot away from immigration reform in 2008. He simply cleaned up his messaging. While the bills he supported in 2006 and 2007 always put border security first, the average voter didn't understand that, and the rhetoric clearly mattered. The American people won't support reform until the government gets serious about securing our borders. This was the big lie of the 1986 amnesty — if we give citizenship to everyone, we'll secure our borders. That never happened. If you actually look back at the 2008 town halls, McCain said we need to secure the border first and then deal with the other parts of reform. That's consistent with the 2013 bill, his position in 2010 and today. Additionally, maybe ironically, this argument now appears to be consistent with Mr. Trump's position. What is clear about the dynamics of the immigration debate is that pro-reform politicians are losing the messaging fight. Yelling "amnesty!" is much easier than outlining thoughtful proposals, but ultimately, thoughtful proposals are what are needed to resolve this sticky issue.  

FIX: You were brought on to House Speaker John A. Boehner’s staff in 2013 to lead an immigration push. It never came. What happened?

Tallent: The fact was that the House Republican Conference just didn't trust President Obama to enforce the laws as written by Congress. President Obama and his administration have a consistent record of trying to work around, not with, Congress to push his agenda on issues like land use, energy policy, health care and on and on.  Republican members of Congress just didn't trust this administration to follow through on immigration proposals to actually secure the border and enforce our immigration laws before moving forward with a mass legalization program. The White House was made aware of this trust deficit and then just days later waived another mandate under Obamacare. So the question is, were they tone-deaf to the concerns, or were they just not willing to work with Republicans in Congress to get an honest deal done? I guess we'll never really know.

FIX: Is there a Republican majority in Congress for any sort of comprehensive immigration reform plan? If so, what does that look like? How do you thread that needle?

Tallent: Comprehensive reform as the Senate proposed it in 2006, 2007 and 2013 will never receive majority support of House Republicans. Post-Obamacare, the American people and particularly Republicans just don't trust massive, 2,000-page pieces of legislation. Speaker Boehner had a realistic proposal for getting reform done, a series of bills building off each other that brought a majority of players and interests to the table. Individual pieces will need to deal with enforcement and border security, high-skilled workers, agricultural labor needs and legalization. Each of these bills will need to be simple and easy to understand by both those that are affected by the new programs and everyday Americans. This was the fatal flaw with the 2013 legislation passed out of the Senate. It was too complicated. It tried to make everyone happy, and ultimately, no one understood it or trusted it. Congress needs to get back to the basics and deal with the specific problems at hand with legislation that can restore order to the chaotic system we're currently living with. If those are the types of common-sense legislative proposals put forward, a majority of Republicans can support that.

FIX: Finish this sentence: "Comprehensive immigration reform that deals directly with the 12 million people here illegally will pass Congress ____________." Now explain how that comes about.

Tallent: "…when the American people demand it."

Advocate groups and traditional allies can run themselves ragged, but until the everyday voters, including those in predominantly Republican districts, call for reform, it just isn't going to happen. Pro-reform Republicans need to figure out a way to reach beyond the traditional advocates and allies to the small business owners in their districts and the people sitting in the church pews. Members of Congress like Mick Mulvaney [of South Carolina] and Raúl Labrador [of Idaho] have the ability to do that. Hopefully they will continue to be involved in this conversation.