Pollstering is an uncertain art at best. There's an old saying in military circles that "...we are always training to fight the last war," and I suspect the same is true for pollsters; they are always using methods adapted for the last election, and boy howdy, could that ever trip them up this time, as this is an election like none other in living memory. On Monday, one senior GOP strategist, Alex Castellanos, who worked on the presidential campaigns of Jeb Bush and Mitt Romney, thinks there are indicators the pollsters may be overlooking.

He may be right. But I think there is something Mr. Castellanos is overlooking, as well.

Pollsters have been getting it “wrong” in the final days of the 2024 presidential race by overlooking a “massive shift” in voter registration since the last election — which could tip the scales in favor of former President Donald Trump on Tuesday, a veteran GOP strategist says.

Alex Castellanos, who has worked on campaigns for Jeb Bush and Mitt Romney, told Fox News’ “Special Report” that the polls — which show a razor-thin margin between Trump and Vice President Kamala Harris — are disregarding a “wavelet out there of Republican enthusiasm.”

“What I think they’re missing is a massive shift in voter registration underneath all of this. Thirty-one states have voter registration by party. Thirty of them in the past four years have seen movement toward Republicans,” the longtime strategist said late Sunday. 

This has been reported before, of course, and for pollsters to have not taken this shift in voter registration into account would be, honestly, incompetent. But remember what I said about training to fight the last war?

The two wavelets Mr. Castellanos refers to go hand-in-hand, of course; there is such a thing as the zeal of the convert, and it applies to politics as well as in many other areas. And pollsters may be underestimating that.

“I think there’s, I’m not going to call it a wave, but I think there’s a wavelet out there of Republican enthusiasm and registration. If I register to vote Republican, whether I’m switching or new, what am I going to do?”

Castellanos suggested the failure to recognize that boost was to blame for the lack of statistical variation in the polls coming out in the final stretch before Election Day. 

“I think the pollsters are getting this wrong. We’re all missing something, because they’re giving us the same poll over and over again. There isn’t even statistical variation,” Castellanos said.

But here's the thing that the early-voting numbers and the polls alike may not be capturing: Trump Democrats.

See Related: Inspiring Tucker Carlson Ad Tells Tale of the American People and the Importance of Voting for Trump

WATCH: ABC's Stephanopoulos Spews Final Melodramatic Bilge About Consequences of Election Results

There have always been cross-over voters. My Dad always said he was a Truman Democrat (although he and Mom were always registered as Independent), but if so, then in the '80s, Mom and Dad both were also solid Reagan Democrats, a member of the group that helped propel the Great Communicator to his 1980 win and, even more so, to his 1984 landslide reelection, where he gained more electoral votes than any presidential candidate in American history. There are, without doubt, registered Democrats today who will vote for Trump/Vance. Oh, sure, there are Republicans who claim they will vote for the Harris/Walz slate, but we can talk about Liz and Dick Cheney another time.

That's the real test of the polls this election - are they capturing this cross-over vote? We will soon have some indicators - very soon. Tomorrow, in fact. Once that's over, all the pollsters can stop, take a moment, catch their collective breath - and start training to fight the last war, all over again.