(CNN) For the first time in nearly 10 years, a sitting US senator is on trial on bribery charges.

Sen. Bob Menendez, a New Jersey Democrat, is accused by federal prosecutors of accepting lavish vacations and hundreds of thousands of dollars in campaign donations from Dr. Salomon Melgen, a Florida-based ophthalmologist . Opening arguments are scheduled to begin Wednesday morning in Newark federal court.

Here is what to look out for as the case gets underway:

Will Sen. Menendez or Dr. Melgen take the stand?

The case hinges on the relationship -- friendship or otherwise -- between Menendez and Melgen. While there has been no indication that either could take the stand from court documents filed so far, it's plausible that the defense could call the pair individually to the stand to describe their relationship.

The pair, which the defense has described in court documents as "close friends," are painted by federal prosecutors in court documents as co-conspirators with a quid-pro-quo relationship. Melgen was described in a recent prosecution brief as Menendez's "patron."

Will the pair use a McDonnell defense?

In proposed juror instructions filed by the defense over Labor Day weekend, attorneys described the high legal bar for the charges brought by the Justice Department against the men.

That's partially because a Supreme Court decision last year set a new standard for what qualifies as an "official act" in a government corruption case. The justices clarified that simply hosting an event for someone doesn't constitute an official act -- the official has to put his thumb on the scale in an ongoing proceeding or pressure someone else to do so.

Former Virginia Gov. Bob McDonnell, a Republican, had initially been found guilty of corruption charges arising from gifts, money and loans from a Virginia businessman. But the Supreme Court unanimously overturned the verdict , raising the bar on what qualifies as an "official act" in this type of case. Defense attorneys may claim that the interactions between Melgen and Menendez do not rise to that level.

What is Harry Reid's role in all of this?

Last week's trial brief filed by prosecutors referenced a phone call by Menendez to then-Senate Majority Leader Harry Reid to ask for help in a Melgen-related issue. Melgen had been slapped with a decision by the Centers for Medicare and Medicaid Services that he had overcharged Medicare for $8.9 million for a retina-related treatment. According to the brief, after Melgen requested Menendez's help with the situation, Menendez reached out to a variety of federal officials, including Reid, for assistance.

According to prosecutors, Reid also reached out to an unnamed White House official for further assistance. The prosecution claimed in last week's trial brief that they will call former Menendez staffers to testify in the case. Could they also call Reid or the unnamed White House official?

Will Menendez show up to court every day?

In pre-trial proceedings, Menendez's team fought hard for the court to accommodate his schedule, even requesting that the court delay proceedings until October to accommodate the start of the Senate session Tuesday -- the day before the trial is due to commence. Defense attorneys argued in another filing late last week that the court needed to adjourn on certain days so that Menendez could return to Washington for "critical votes." That idea was sternly dismissed by federal judge William Walls , who will hear the case.

"The court suspects that the trial strategy behind this motion, if granted, would be to impress the jurors with the public importance of the defendant senator and his duties," wrote Walls in the opinion published Friday."

But according to Walls, Menendez does not need to come every day.

"If the senator wishes to absent himself at times for purposes of vote, that is his prerogative and I have no problem with that," Walls said during a hearing last month.

What does this mean for Democrats on a national scale?

Democrats have not commented publicly in recent days on the case, and in the weeks preceding the trial, Menendez has held a variety of public events in New Jersey.