Why Are Four Republicans Speaking On Opening Night Of The DNC?

The Democratic National Convention features an unusual lineup with Republicans like John Kasich speaking, emphasizing bipartisanship. The Lincoln Project, an anti-Trump group, criticizes the president, while the convention aims to appeal to silent Biden voters. Despite some Democratic discontent, Kasich's support in Ohio could be pivotal for Biden.

What does the theme 'We, the people, putting country over party' suggest about the convention's message?

In what way could John Kasich's support impact Biden's chances in Ohio?