Bill Clinton once explained the nation’s two political parties by saying that Democrats want to fall in love while Republicans want to fall in line.

That adage has not withstood the Trump era. Today, it is Republicans who are besotted.

Donald J. Trump’s decisive victory in Iowa revealed a new depth to the reservoir of devotion inside his party. For eight years, he has nurtured a relationship with his supporters with little precedent in politics. He validates them, he entertains them, he speaks for them and he uses them for his political and legal advantage.

This connection — a hard-earned bond for some, a cult of personality to others — has unleashed one the most durable forces in American politics.

Iowa Republicans, following the lead of party officials across the country, rallied behind the former president despite a list of reasons to reject him. Republicans lost control of the presidency, the Senate and the House during his four years in office. He failed to deliver the red wave of victories he promised in the 2022 midterms. He has been charged with 91 felonies in four criminal cases this past year.