The heated Senate Republican primary in Texas will continue for several more weeks, with NBC News projecting that Sen. John Cornyn and state Attorney General Ken Paxton will advance to a runoff. Prediction markets are pricing in a complete reversal of expectations — the incumbent Cornyn had received 43.2% of the vote compared to 39.9% for the challenger Paxton, but traders now see Paxton as the overwhelming favorite to finish second, jumping from 6¢ to 96¢ overnight.

The market shift reflects "The runoff will be the hardcore primary voters, and that's his base," Miller said, "so he'll be extraordinarily difficult to defeat in a runoff." Meanwhile, traders are pricing Cornyn's margin of victory at just 0-3% (86¢, up from 4¢), suggesting the incumbent senator's path to a fifth term has narrowed dramatically. The Texas primary for the U.S. Senate has become the most expensive Senate primary contest in state history. As of mid-February, the tracking organization AdImpact Politics reported that spending in the Republican and Democratic races combined had reached close to $99 million.