Including dismissal without a trial.
RE: According to the constitution, the Senate may make whatever rules they like.
Article I, Section 3, Clauses 6 and 7 provide:
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside:
And no Person shall be convicted without the Concurrence of two-thirds of the Members present.
Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States; but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.
Here's the bottom line: there are only a few sentences in the entire constitution relating to impeachment. It's completely uncharted territory, and as it's only happened twice before Trump, there's no real precedent. Even more interesting, the two prior occurrences never established - as a rule of common or codified law - any binding precedence either.
That's why the House was able to strong arm their articles through committees and the floor vote. Since impeachment isn't a criminal indictment, there wasn't any allowance made for defense witnesses, nor effective cross of DNC (hearsay) "witnesses". So what the House has effectively proved is that anything goes.
Well, now it's time for the Senate to have its turn at the wheel of fortune. And what's good for the goose is good for the gander. The constitutional stipulations are incredibly loose and vague. Really, the Senate can literally do anything they want, including treating the published articles as 'delivered'. There is simply nothing that could stop the Senate from dismissing the entire cause of action without even holding a hearing.
Since this is the case, and the Senate holds all the cards, it's like a cat toying with a mouse. There is no out option for the House on this any longer; their pinnacle point of power when was when the last vote was cast in favor. Like a girl playing hard to get, once the deed is done, the power shifts hands.