WASHINGTON — In a stunning, public attack on his own party leader, Republican Sen. Ted Cruz accused Majority Leader Mitch McConnell of lying, and said he was no better than his Democratic predecessor and couldn’t be trusted.

Cruz, a Texan who is running for president but ranks low in early polling, delivered the broadside in a speech on the Senate floor Friday, an extraordinary departure from the norms of Senate behavior that demand courtesy and respect.

“Not only what he told every Republican senator, but what he told the press over and over and over again, was a simple lie,” Cruz said.

At issue were assurances Cruz claimed McConnell, R-Ky., had given that there was no deal to allow a vote to renew the federal Export-Import Bank – a little-known federal agency that has become a rallying cry for conservatives. Cruz rose to deliver his remarks moments after McConnell had lined up a vote on the Export-Import Bank for coming days.

“It saddens me to say this. I sat in my office, I told my staff the majority leader looked me in the eye and looked 54 Republicans in the eye. I cannot believe he would tell a flat-out lie,” Cruz said.

“We now know that when the majority leader looks us in the eyes and makes an explicit commitment that he is willing to say things that he knows are false.”

The majority leader was not on the Senate floor when Cruz issued his attack, and ignored reporters who tried to ask him about it in the Capitol’s hallways. A spokesman said McConnell would have no response.

McConnell has long indicated he would allow a vote on the Export-Import Bank as an amendment on the highway bill, which is the course he’s now following. Senate supporters of the Export-Import Bank have said they got that commitment from McConnell in the course of debate on a separate trade bill, though there’s been some dispute about what precisely was agreed to.

No senator rose to defend McConnell on the floor, as some Republicans sought to avoid engaging in the dispute and giving Cruz still more attention. Questioned by reporters later, Sen. Orrin Hatch, R-Utah, challenged Cruz’s criticism of McConnell, telling reporters, “I think it’s wrong to disclose private information, especially when the disclosure is not accurate.”

“Keep in mind, he’s running for president,” Hatch added. “People who run for president do some very interesting things.”