Republican front-runner Donald Trump has given some braggadocious victory speeches in the past, but his remarks after New York's primary on April 19 showed a newly polished, presidential candidate. Here's a look at his changed style. (Jenny Starrs/The Washington Post)

Remember when cable networks were giving Donald Trump half the total airtime for all the candidates in the Republican primary? Those were wild times, and, they're over.

Now, Trump's share of the GOP airtime is up to 70 percent.

But his national poll numbers aren't rising accordingly -- suggesting there's only so far that free media can take Trump in this campaign.

Those stats come from the GDELT Project, using data from the Internet Archive, which tracks how often various candidates are mentioned on cable news channels. Trump has dominated television coverage since he entered the race last summer, among Republicans and presidential candidates overall. If you consider all exposure to be good exposure for a candidate, the disparity has given Trump a huge financial edge on his rivals; some pundits have suggested it's the reason Trump jumped to the top of the field in the first place.

If TV made Trump so popular, it might follow that more TV would only make him more popular. That does not appear to be the case, notwithstanding Trump's blowout win in the New York primary Tuesday night.

Trump's cable exposure, as a share of the Republican field, hit a trough in early February, when he dipped below 40 percent of all candidate mentions. Since then, it has doubled. Over the past 30 days, Trump has commanded 70 percent of GOP candidate mentions, which rises to 75 percent if you throw out mentions of candidates who quit the race.

Trump's poll numbers have risen over that period, but not by nearly as much, per Real Clear Politics:

There are many possible explanations for what's going on here. Perhaps paid television advertisements are finally asserting themselves as a force in the GOP race; his opponents and outside groups have barraged Trump lately with attack ads, after all. That barrage was largely absent in New York, which may be a factor in why he won so handily there.

Perhaps Trump has hit some natural "ceiling" of support in the electorate -- other folks won't vote for him no matter how often he pops up on CNN. Perhaps not all coverage is good coverage, and voters might be reacting poorly to what they see and hear about Trump onscreen.

Republican presidential candidate Donald Trump speaks during a campaign event at the First Niagara Center in Buffalo, N.Y., on April 18, 2016. (Photo by Jabin Botsford/The Washington Post)

Or perhaps his high TV coverage was never the best way to explain Trump's lead in the first place.

None of those explanations excuses the disparity in coverage. Ted Cruz, for example, retains a good chance of beating out Trump for the nomination. In the past month, he snagged less than 15 percent of GOP cable airtime. That's a disservice to Cruz and to voters.

Cable producers don't need to look far for an example of how to conduct fair coverage in a tight race. They have one, in the Democratic primary. Bernie Sanders closed to a dead heat with Hillary Clinton over the past month in national polls. Guess what happened to their TV time?

Donald Trump claims he's treated unfairly a whole lot. Here are just a few of the times he said he wasn't getting his due. (Peter Stevenson/The Washington Post)