Republican presidential candidates Marco Rubio, Donald Trump, John Kasich and Ted Cruz feuded over rhetoric, elections and immigration at the March 3 debate in Detroit. Here are the key moments. (Sarah Parnass/The Washington Post)

One side effect of the agitation over an imminent Donald Trump nomination is the emergence of a litmus test for prominent Republicans. Would you or wouldn't you support the Republican nominee for president if it is Donald Trump, Trump’s opponents in the process were asked during the debate on Thursday, with each of them saying yes — even Marco Rubio, who sells merchandise on his campaign website that says, “Never Trump.”

There are political science (and/or psychology) dissertations to be written on why these candidates won’t simply cross the line into declaring Trump ineligible; one can only assume that they have polling data that suggests it will shave off a few supporters at a time when they're desperately trying to snowball their way to a surprise win.

But that’s not what we’re here today to talk about. Instead, we’re here to talk about the version of that question that was posed to Trump himself. “Can you definitively say tonight that you will definitely support the Republican nominee for president,” Fox News’s Chris Wallace asked, “even if it's not you?”

Trump’s response:

Let me just start off by saying that I’m very, very proud of — millions and millions of people have come to the Republican Party over the last little while. They’ve come to the Republican Party. And by the way, the Democrats are losing people. This is a trend that’s taking place. It’s the biggest thing happening in politics, and I’m very proud to be a part of it.

It’s a classic pointillist answer from Trump — a few dabs from a few different places resulting in one heck of a portrait. But it’s not really true.

We looked earlier this week at whether Democrats were bailing on their party, as Trump suggested. Turnout is down in the Democratic contests, though that may be a function of there being a much more dominant front-runner. There’s little indication that Democrats are jumping ship to back Trump in large numbers, though of course that’s happening. (As it is happening in the other direction, too.)

A report from the Boston Herald before Super Tuesday cited the Massachusetts secretary of state’s office to note that 20,000 Democrats had left their party before voting began. A representative from the secretary of state's office confirmed to The Washington Post by email that this had happened — with 16,000 of them switching to be independents, not Republicans. That’s out of about 1.5 million Democrats in the state, incidentally.

The state of Texas, the largest to vote so far this year, added about 250,000 new voters since November of last year — but that’s all voters, not just Republicans. We can’t tell from the state’s data how many are Republicans. In California, the largest state, Republican voter registration is “tanking,” in the words of the Los Angeles Times, with the density of Republicans in the voter pool falling 3 percent since 2012. What Trump giveth, Trump taketh away.

Gallup’s regular polling on party identity doesn't see much of a spike for Republicans either.

It is true that more than a million more people have voted in the Republican primaries and caucuses so far this year than the Democratic ones. But that has nothing to do with "com[ing] to the Republican Party."

A better way of looking at that claim is to consider how many new voters are turning out. This is hard to measure without full access to state voter files, but we can estimate.

For example, exit and entrance poll data reported by CNN tells us about how many of the people who’ve come out to vote in that party's elections this year are first-time voters. Forty-four percent of voters in Iowa were doing so for the first time, compared with 16 percent in New Hampshire and 20 percent in Texas. The high was 62 percent in Nevada — one of the few states where Democrats turned out more heavily than Republicans. Adding it up, we get about 1.1 million people on the Democratic side who’ve come out to vote for the first time in a primary in 2016.

That’s not necessarily new voters. Democrats have a habit of voting only in the general election and skipping the primaries. But it’s an estimate.

We can also estimate how many of those people came out because of Bernie Sanders, the unexpected candidate who’s doing well with new voters on the Democratic side. In states where there were enough new voters for their vote preferences to be statistically significant, about 563,000 of those new voters backed Sanders. It’s safe to assume that he got about another 100,000 from the states where there were too few new voters to break out this measure separately. So, figure that Sanders spurred about 650,000 people go to the polls. That's out of 6.2 million total voters. Impressive.

On the Republican side, the math is trickier. First and foremost, exit and entrance polls in most states didn’t ask Republicans whether it was their first time voting, only doing so in New Hampshire and Iowa. In those two states, about 127,000 people were voting for the first time, and about 42,000 of those were voting for Trump. That’s actually lower than the number of new voters in Iowa and New Hampshire that backed Sanders; he got about 68,000 votes from new voters in those two states.

That’s the second reason the math is tricky. Sanders has accrued 37.5 percent of all of the Democratic votes, to Trump’s 34.5 percent of the Republican one. (All vote result data is from the irreplaceable U.S. Election Atlas.) Sanders is trailing in the delegate count by a lot, and Trump is winning by a lot — but there are two Democrats and four Republicans. And there are four Republicans now; just over a month ago, there were still a dozen to split up the vote. In Iowa and New Hampshire, Trump got 30 and 38 percent of the new vote, respectively. Sanders got 59 percent and 78 percent.

So it seems safe to assume that, even with increased Republican turn-out, the number of new voters voting for Trump isn't much higher than the number backing Sanders. It’s hard to believe that it has reached 1 million, much less “millions and millions.”

There is one way in which Trump might be spurring “millions and millions” to the early-voting states. If about a quarter of the electorate in the early states has been new voters, as on the Democratic side, that means that 2.3 million people voted for the first time through Super Tuesday. Millions and millions. And a some large chunk of that group was indeed turning out because of Trump.

To vote against him.