Following Ted Cruz's loss to Republican front-runner Donald Trump in all five state primaries last Tuesday, unbound delegates are beginning to rethink their support for the Texas senator,These delegates, particularly in North Dakota, where Cruz declared victory after filling 18 of 25 unbound delegate slots on April 3, are vital to Cruz’s quest to deny Trump the 1,237 delegates he’ll need on the first ballot at the Republican National Convention in Cleveland.But friendly delegates are as subject to shifts in the race’s momentum as anyone else, and Cruz’s strength with some of these crucial first-ballot convention voters may be overstated.With Trump's recent decisive victories, many of the delegates, wary of a bitter convention battle that could tear the party apart, are rethinking their commitment to the Texas senator.Of the 10 North Dakota delegates on the Cruz slate reached by National Review, five expressed serious reservations about backing the Texas senator on that crucial first ballot.With Trump on a winning streak that’s seen his popularity and electoral success continue to grow past the long-assumed "ceiling" of 35 to 40 percent of the Republican electorate, many North Dakota delegates who privately support Cruz are rethinking the wisdom of challenging the real-estate mogul’s commanding lead on the convention floor.Rick Becker, a former North Dakota gubernatorial candidate who is still loyal to Cruz, says one delegate who he believes would like to support Cruz is nevertheless warning peers about the damage they could do to the party’s November prospects by angering the millions of voters who support Trump.