Kasich is mathematically eliminated from the nomination. Even if he sweeps all the remaining states and wins all the remaining delegates he does not have enough to meet the 1237 threshold. The best that Kasich can do is hope for a contested convention and that he would be the unity candidate. But even that is a pipe dream. It is highly unlikely that he will win another state, let alone come into the convention with a plurality of delegates. All he can do is play a spoiler but not to Trump, a spoiler to Cruz.
So what can the Cruz campaign do to convince Kasich voters to not waste their vote? How do you write an ad addressing Kasich voters without talking down to them, insulting them, or attacking Kasich? To do that Cruz needs to understand who these voters are and why they still want to go for Kasich. They are probably not hard core conservatives otherwise they would be for Cruz (and in some cases, Trump). Not only do they not like Trump, they are also probably uncomfortable with Cruz either because of his positions or his reputation. Drafting an ad appealing to Kasich primary voters but not turning off Cruz base supporters is a big challenge.
How do you make Kasich voters comfortable enough to voter for Cruz without turning off the conservative base? If you haven’t guessed from the title, I propose drafting Kasich as the VP. Would it work? We can turn to history to get an idea. In 1980 Reagan faced a similar challenge, although at a different point in the campaign. He had the nomination sown up but there was still a large faction of non-conservative voters who could have been flipped in the general election. They had rallied around George H. W. Bush as their champion. Reagan didn’t want to change his positions but he needed those voters. To reassure them, he picked Bush for his VP. The pick let the moderate know they had a voice in the administration. At the same time, Reagan effectively eliminated his opposition leader by co-opting him. The rest is history.
Kasich could play that same role. Cruz picking Kasich is the best way to reach Kasich voters without turning off the Cruz base. Kasich voters will know that they have a voice in the Cruz administration. For Cruz, it removes Kasich as an option on the ballot leaving only Cruz as the anti-Trump. Even though Cruz and Kasich have different positions on some issues, Cruz has not attacked Kasich so he still has some appeal to those voters. It also should not turn off that many Cruz voters. There will be some calls that he is selling out, but that is simply not the case. Cruz is still the top of the ticket and he does not have to change any of his positions. He still calls all the shots.
On top of it all, Kasich is a decent pick for VP. He is governor of an important state that we need for the general election and is popular enough to win the GOP primary there. He is an experienced politician having been in congress as well as the Ohio governor. His voting record could be better but he is not an extreme liberal. In the end though, he is the VP which does not have a lot of power or influence. There are probably better candidates out there, but the need to stop Trump outweighs those considerations. It is about the only sure fire way of getting him out of the race.