For months, Democrats have been watching the GOP presidential primaries with a mixture of amazement and glee, as Republicans went through the process of chaining themselves to an egotistical bully with a disdain for facts and a penchant for statements seemingly designed to alienate major voting blocs. Victory was assured. Democrats only had to ponder how big their triumph over the unelectable Donald Trump would be: Big enough to capture states that have been Republican strongholds, such as Arizona and Georgia? Big enough to deliver Democratic control of the Senate — or even the House? Big enough to cause a fatal splintering of the Republican Party?