Liz Cheney election campaign asks voters to change their party affiliation in order to vote for her

When I first learnt about this a few days ago, I thought this cannot be true. This must be some kind of a political smear campaign or the like.
Was I wrong!

This actually raises serious questions about election integrity. How often do such manipulative political party affiliation switches occur to help or even determine who becomes a political candidate on the ballot?

E.g. what if this switching by opponents is well organized to target specific candidates?

Vote For Liz - Liz Cheney