Primaries To Watch: GOP Fears Ohio Upset; Trump And Ocasio-Cortez Back Challengers

President shakes hands with Ohio 12th District Republican nominee Troy Balderson during a rally last weekend in Lewis Center, Ohio.

John Minchillo / AP

A critical House special election on Tuesday could provide some of the biggest clues yet about how much trouble Republicans could be in this November.

In Ohio, the last Republican vs. Democrat matchup before November has become the latest proxy fight for whether Democrats can harness the energy, activism and overperformance in past special elections to pull off an upset in a GOP-held district.

Republicans, meanwhile, have brought in President Trump himself and millions of dollars to stop that from happening, which would further trigger alarm bells about a possible blue wave in the fall midterms.