The road to Pence’s half-hearted yes was an agonizing one. He loathes Trump, and genuinely believes that Cruz and Trump are fighting for the soul of the Republican party. Echoing Ronald Reagan’s endorsement of Barry Goldwater in 1964, he said Wednesday that the race represents “a time for choosing.” So the choice for him was always between backing Cruz and staying on the sidelines. But sources familiar with his decision say his advisers by and large counseled him against an endorsement, arguing it would hurt his chances in a tough reelection battle this fall, and the 2016 race has certainly raised the question of how much endorsements matter. At the same time, Pence came under intense pressure from conservative donors, politicians, and media figures — many of them close personal friends — to back Cruz. The result was a lukewarm endorsement that left both sides unsatisfied.

Over the last two weeks, as Trump racked up a series of devastating primary victories and Cruz’s poll numbers began to slip in Indiana, Cruz and his allies began pressing Pence to endorse. The drumbeat reached a crescendo on Wednesday evening, at a Pence fundraiser hosted by the Ricketts family at Chicago’s Wrigley Field. Joe Ricketts, the Chicago Cubs owner and TD Ameritrade founder, is also funding the anti-Trump group Our Principles PAC. In a ballpark suite, several people gathered to help Pence’s reelection efforts, including Wisconsin governor Scott Walker and Nebraska governor Pete Ricketts, pressed Pence to endorse Cruz, according to a source familiar with the event. Walker proved a crucial ally for Cruz in the run-up to Wisconsin’s April 5 primary, campaigning with the senator and cutting ads on his behalf. The Wall Street Journal has reported that Ricketts himself is also expected to endorse Cruz ahead of Nebraska’s May 10 primary. A spokesman for the Ricketts family, Brian Baker, declined to comment.