During this segment of the Senate Impeachment Trial, the opposition and the Senators are not permitted to raise objections. They must stand mute. Even the Chief Justice has to remain mute, just listen. The managers are free to say what ever they want.
Really - can you point to the appropriate federalist paper for that insight? Because, on the contrary, what we're witnessing is **exactly** what the founders predicted if impeachment were to become a purely partisan political tool.
Which brings up another point: because the Trump impeachment is an entirely political affair, rules & procedures fall not under standard legal doctrine, but rather stay firmly entrenched with the political domain. That means anything that typically occurs during a campaign, including lying, slander, libel, fabricating evidence, making false claims - the whole gamut of "dirty tricks" - are all fair game. And if you don't believe it, then why did the senate adopt rules that allow exactly this kind of behavior?
What people should be paying attention to is the game within the game. That is, after the GOP is finished with it's allotted time and the "trial" wraps up with acquittal, the real fun & game begin. There are literally hours of footage available to use for commercials, to fine tune for bullet points, and to flood the media with particular spin. That's why this impeachment was invoked; not to remove Trump, but to possibly defeat him. And barring that, perhaps hold the house and/or gain the senate, from which they can stall his agenda.