NEW YORK >> NBC News’ coverage of the first Democratic debate of the 2020 campaign season Wednesday was marred by a technical glitch that led President Donald Trump to tweet that the network “should be ashamed.”

The snafu, in the middle of the debate, left viewers and candidates confused by crosstalk apparently caused by a failure to turn off the microphones of NBC personalities who had left the stage.

Otherwise, NBC ran a substantive, fast-moving debate that occasionally veered off course, primarily due to 10 candidates eager to make the most of limited time. Ten more Democratic candidates will take to a Miami stage today for a second session, also televised on NBC, MSNBC and Telemundo.

NBC’s technical problem came following a halftime switch from Lester Holt, Savannah Guthrie and Jose Diaz-Balart — who were the primary questioners in the first hour — to Chuck Todd and Rachel Maddow. Todd was interrupted by voices as he tried to direct a gun control question to Massachusetts Sen. Elizabeth Warren.

It caused a brief, uncomfortable period of confusion before Todd switched to a lengthy, unplanned commercial break.

“We prepared for everything,” Maddow said. “We did not prepare for this.”

Following the break, the issue was corrected. But it gave Trump, who had earlier critiqued the debate as “boring,” an opening to attack one of his favorite targets, the news media.

NBC and MSNBC “should be ashamed of themselves for having such a horrible technical breakdown in the middle of the debate.” He called it “truly unprofessional.”

NBC did not have an immediate response to the president.

The network’s ground rules set up a question-and-answer session more than a debate, with candidates given 60 seconds to respond to a question and 30 seconds to address a follow-up. Guthrie quickly used a follow-up to point out that former Texas Rep. Beto O’Rourke hadn’t answered her question about tax policy.

In the early stages, the candidates followed the rules — until New York Mayor Bill de Blasio jumped into the discussion on tax policy without being asked a question. The NBC moderators did not cut him off. He did the same thing again successfully but was stopped a third time by Guthrie because the network had to cut to a commercial.

That led to some confusion throughout the debate over how aggressively NBC would police the candidates when they interrupted others. It was often a hard call, because letting the candidates go after one another produced some of the more compelling moments, such as when O’Rourke and former housing secretary Julian Castro argued over immigration policy.

Perhaps surprising was how little Trump was brought up, as the candidates discussed health care, gun control, climate change, economic policy and the confrontation with Iraq.

NBC tried to involve all 10 candidates but inevitably didn’t satisfy everyone. Hawaii Rep. Tulsi Gabbard’s Twitter feed, in a post apparently written by her sister, wrote that “it’s clear who MSNBC wants to be president: Elizabeth Warren.”

Warren was asked the first question of the debate, and again in the second hour. She was also given the last word of the candidates when they gave closing statements.

But the FiveThirtyEight blog reported that New Jersey Sen. Cory Booker spoke the most words, 2,181, during the debate. O’Rourke was second with 1,932 and Warren was third with 1,637. Gabbard finished seventh among the candidates in words spoken, with Washington Gov. Jay Inslee last.