Any day that voters are voting -- in this case in primaries in Virginia, North Dakota, South Carolina, Maine and Nevada -- CNN's Chris Cillizza and Harry Enten like to talk. Or, really, email. Below, their email conversation about what to watch for in today's primaries -- plus a revealing insight into Harry's college life!

Chris: Harry! Shalom!

It's a primary day! Five states voting -- NoDak, South Carolina, Virginia, Nevada and Maine.

We could start almost anywhere (I am partial to the Maine "ranked choice" innovation) but since you are younger and more handsome, I'll let you pick. What storyline intrigues you the most -- and why?

Harry: Shalom Christopher!

Mathematics indicates that I am younger. Looks, however, are in the eye of the beholder.

You know it's not quite Friday yet, but Tuesdays are like an electoral sabbath, so forgive me when I say Good Shabbos.

What you may not know about me is that in college I took a number of courses on alternative voting systems. I even created my own voting system called Borda Approval Voting. My professor Bob Norman for that course, who has to be in his mid-nineties now, is still going strong at last check. He also helped me fix a broken ribbon on my manual typewriter. What a guy.

So I think Maine is very interesting to me. Will people get confused? Will it change any outcomes? There's also a people's veto on the ballot to try and start the process of getting rid of it. Many Republicans, including Gov. Paul LePage, don't like the system. (Interestingly, my former professor doesn't like it for other reasons.)

My big question is if the people's veto doesn't go through and voters like the system, will it start a trend in other states? One of the ways we are most "federalist" in this country is voting. Some states have runoffs when no reaches a majority (pretty much all in the south). Some states split their electoral votes.

The sky for differentiation and potential confusion among voters (a key complaint about ranked choice) is limitless.

Chris: Of all the people on earth -- literally, all of them -- who might tell me they created alternative voting systems, I am the least surprised that you did so. Like, not at all. (For more on Borda voting, and other alternative voting options, : Of all the people on earth -- literally, all of them -- who might tell me they created alternative voting systems, I am the least surprised that you did so. Like, not at all. (For more on Borda voting, and other alternative voting options, read this .)

So, let's backtrack slightly before we go forward.

On Maine's ballot for governor (and a few other races) today, voters will be asked to rank their choices -- from one to whatever. If no candidate in the race gets a majority of the vote, the last-placed candidate will be eliminated and his/her votes will go to the candidate they marked as their second choice.

It's an interesting idea! But not to Maine's governor! Paul LePage called ranked choice voting "the most horrific thing in the world," which feels to me like at least a slight exaggeration.

I also am intrigued by Mark Sanford's primary problems in South Carolina. Voters in the Palmetto State seemed totally good with the fact that Sanford, as governor, lied about his whereabouts for several days to cover up an extramarital affair with an Argentine woman. Or, maybe better put, they didn't care enough not to reelect him to his old House seat in 2013.

But, now Sanford has done something that Republican primary voters might not forgive him for: Not supporting Trump enough of the time. Sanford has been what I would describe as mildly critical of Trump but his primary opponent -- a state senator named Katie Arrington -- has gained considerable traction by painting Sanford as a traitor to the Trump cause.

Just hours before polls closed on Tuesday afternoon, Trump endorsed Arrington in a blistering tweet aimed at Sanford.

Harry: Nice link there. I used to say this about myself: once you get to know me, I'm not very surprising.

One last thing I'll note about ranked choice is that it doesn't guarantee that a majority of the voters selected said candidate. It's just a majority of those who cast a vote up to whatever spot on the ballot. That means if someone doesn't fill out their ballot completely, someone can win with the support of less than a majority of the voters backing them (a nerdy paper on it here ).

So many Appalachian Trail jokes to be had about Mark Sanford. I won't make one here, but I would say that he did win by less than you might expect in 2013, given the partisan lean of his district.

You do a good job outlining Sanford's troubles with Trump. It's noteworthy that he actually backed Trump in 2016, unlike others. It's just that support wasn't great enough to some. If Sanford were to go down in flames this evening, I'd say it was his anti-Trump sentiment that put his challenger over the top. But keep in mind, he only won by about 4,000 votes in his 2016 primary. Put another way, not being pro-Trump enough wasn't all that has Sanford in trouble, but it's plenty of it.

Interestingly, South Carolina also has a pretty hot GOP gubernatorial primary, if you've been paying attention... Christopher.

Chris: I am always paying attention. And are we talking about Henry McMaster? I assume we are.

He's sort of the opposite of Sanford; McMaster, who took over as governor when Trump tapped Nikki Haley to be UN ambassador, has been a Trump guy since early on. (Which is weird because way back when, he was a John McCain guy. As was Sanford. But I digress.)

Unless I am wrong, the real question is not whether McMaster gets the most votes today but whether he can get over 50% and avoid what could be a problematic one vs. one runoff right? What are the chances McMaster gets past 50 -- and, if he doesn't, who is his most likely runoff opponent?

Harry: That's who we're talking about. McMaster also endorsed Jon Huntsman in 2016. I mean, Huntsman is part of the Trump administration, though it's still quite odd given where I place them all on the ideological spectrum.

I haven't seen any runoff polling, but I doubt McMaster gets to 50% this evening. It's of course possible, but the latest polls I see have him below 40%. The question is whether his runoff opponent is attorney Catherine Templeton or businessman John Warren.

Trump has backed McMaster, which is another interesting test of how much is Trump's endorsement worth? We saw it wasn't worth a whole lot in Alabama, even in a GOP primary. It did seem to help John Cox in California last week.

Speaking of Trump endorsements, I do wonder what is going to happen out in Nevada with Danny Tarkanian...

Chris: Danny Tarkanian: Dude just keeps running for office. And losing.

He seems like he winds up as the GOP nominee in the open Democratic 3rd District in Nevada, right? Based on name ID alone -- his from all his past races and his father Jerry's from the years of being the most hated/loved/feared college basketball coach in the country.

(Sidebar: I was a young teenager during the UNLV Runnin' Rebels period of total dominance. Larry Johnson, Stacey Augmon, Greg Anthony, Anderson Hunt. My god, they were so good. I still don't know how Bobby Hurley and Christian Laettner ever beat them .)

The 3rd District seems like the sort of seat that Democrats HAVE to hold if they want to win the majority this fall. Trump won it by 1 point in 2016. Lose a seat like that one and I can see Democrats coming up short of the 23 they need.

Thoughts? Let's end on your final thought -- so we publish this before the primary day is over!

Harry: I mean, Tarkanian is certainly the biggest name in that 3rd District primary. Remember, Tarkanian was forced out of that Senate primary. : I mean, Tarkanian is certainly the biggest name in that 3rd District primary. Remember, Tarkanian was forced out of that Senate primary. There are some questions over whether Tarkanian actually has Trump's endorsement or no t.

What I do know is that Nevada is a weird, weird state politically. Trump barely lost it in 2016. It's also home to two seats where the GOP are going to try and get on the board: the 3rd and 4th districts. Both seats are controlled by Democrats, but the 3rd District will be vacated by Jacky Rosen (who is running for Senate) and the 4th District will be vacated by Ruben Kihuen (who was accused of sexual misconduct).

The 3rd is a seat, as you note, that Trump won by a point. The 4th is a seat that Trump lost by 5. If Democrats are going to get control of the House, you'd expect them to win seats like these. Just like you'd expect them to win in Virginia's 10th, which is holding a primary tonight and where Republican Rep. Barbara Comstock has got to be one of the most endangered representatives in the nation. Clinton won her district by 10.