Jeb Bush, the former governor of Florida who left the presidential race after the South Carolina primary, endorsed Ted Cruz on Wednesday, becoming the most prominent member of the Republican establishment to support the Texas senator as he tries to slow Donald J. Trump’s efforts to capture the presidential nomination.

The endorsement came as aides to Mr. Cruz, who is unliked by much of the Republican leadership and many of his Senate colleagues, have been courting high-profile supporters to bolster his candidacy. The Cruz campaign has also sought support from Senator Marco Rubio of Florida, who dropped out of the race after losing his home state to Mr. Trump on March 15.

In a statement, Mr. Bush called Mr. Cruz a “consistent, principled conservative who has demonstrated the ability to appeal to voters and win primary contests.”

He added, “For the sake of our party and country, we must move to overcome the divisiveness and vulgarity Donald Trump has brought into the political arena, or we will certainly lose our chance to defeat the Democratic nominee and reverse President Obama’s failed policies.”