Miami - Former presidential candidate Carly Fiorina endorsed Ted Cruz on Wednesday, a surprise move that's likely to boost the Texas senator's argument that he's the sole Republican who can unite the anti-Donald Trump forces.

Fiorina, who dropped out of the race last month after dismal finishes in Iowa and New Hampshire, said she was “horrified” to watch Trump’s rise in the polls, and compared him to the Democratic frontrunner.

“Donald Trump and Hillary Clinton are two sides of the same coin. They’re not going to reform the system. They are the system,” she said.

“It is time to take our party back. It is time to take our government back. It is time to unite behind the one man who can beat Hillary Clinton, who can beat Donald Trump, who can beat the Washington cartel.”

She cast Cruz as the sole conservative champion left in the fight.

"Ted Cruz has stood up and fought for our right to bear arms. He has fought for our religious liberty. He has fought for our sovereignty," she said. "And he has won over and over. He has won."

The former Hewlett Packard chief executive’s surprise endorsement came after a strong week for the Texas senator. He won votes in Maine, Kansas, Idaho and did better than expected in Kentucky and Louisiana.

It also follows a collapse in support for Florida Sen. Marco Rubio, who is also jockeying to be the alternative to Trump. Rubio has only won one state contest, Minnesota, and finished a distant third place in most of the votes over the last week. (He also won the Puerto Rico primary on Sunday.)

Rubio’s performance in Tuesday’s contests were particularly brutal. He lagged far behind Trump, Cruz and Ohio Gov. John Kasich in the Michigan primary. And polls show him trailing Trump in his must-win home state of Florida, which votes on March 15.

"The field has narrowed," Cruz told a cheering crowd of about 400 at a Miami university. "And what is abundantly clear after election after election after election that there is one campaign that can beat Donald Trump over and over and over again. And we will beat Donald Trump over and over and over again."