“And all the polls taken so far of Cruz vs. Trump head-to-head have Cruz winning.”
Yeah well Cruz has been slipping in all the latest polls. The only place where he is holding his own is in Texas. With Jeb dropping out it looks like his votes were split between Trump and Rubio. I suspect the same would happen if Rubio drops out. Cruz and Trump would split the votes. I see Trump winning.
Is it a head-to-head matchup in Texas?
The point of the article is that Cruz leads Trump by 8-15%, head-to-head, according to the polls.
It's a five-man race at the moment.
And as others have suggested, Trump has probably made offers to Kasich, Carson and Rubio to remain in the race.
If you doubt it, consider that Carson has talked about considering being Trump's running mate, despite Trump calling him a pathological liar and comparing him to a pedophile.
Trump offers the carrot first. If that fails, he offers the stick.