Disgraced former Sen. Bob Menendez (D-NJ) was convicted last year on federal bribery and corruption charges, but the start of his prison sentence was delayed until this summer so that he could support his co-defendant wife Nadine during her own trial, which was delayed until March so she could undergo breast cancer treatment.

However, when Nadine's federal bribery trial began on Monday, the formerly powerful senator was a "no-show" at the courthouse, according to the New York Post.

It is unclear why Menendez was nowhere to be seen at the start of his wife's trial, which is especially curious since his prison sentence was pushed back explicitly so that he could attend the proceedings and support her, but one possibility for his absence during opening arguments on the first day is that he may eventually be called to testify on Nadine's behalf by her defense attorneys.

Menendez convicted of bribery and corruption last year

Politico reported last July that then-Sen. Menendez was convicted by a jury on 16 federal criminal counts that included bribery, corruption, extortion, obstruction of justice, and acting as a foreign agent for Egypt and Qatar, as well as conspiracy to commit all of the above, among other things.

He had been federally charged along with his wife and three other co-defendants with a scheme to accept hundreds of thousands of dollars in bribes -- including in cash, gold bars, and a Mercedes-Benz, among other things -- in exchange for him using the considerable power and influence of his position to attain favors for his friends and the foreign governments.

Nadine was supposed to have stood trial with her husband and the three other co-defendants -- two of whom were also convicted while the third accepted a plea deal and testified against Menendez -- but her trial was delayed by the judge so that she could receive treatment following a cancer diagnosis.

Start of prison sentence delayed by judge so he could attend wife's trial

In January, NBC News reported, ex-Sen. Menendez was sentenced by District Judge Sidney Stein to serve 11 years in prison -- roughly splitting the difference between the 15 years requested by prosecutors and eight years sought by the defense -- and was ordered to forfeit nearly $1 million in alleged ill-gotten gains.

Yet, the judge further ruled that Menendez did not need to begin serving that sentence until June so that he could be by his wife's side to continue to support her not only during her cancer treatment recovery but also her trial that had been rescheduled for March.

"I want him to be able to be present for his wife," Stein said during the sentencing hearing.

Indeed, per the Post, there was no mistaking the judge's expectation that Menendez would attend his wife's trial, as that was clearly indicated on multiple occasions.

"I’m going to want to have him able to be present for Mrs. Menendez’s trial," the judge said at one point, and reiterated at another, "I do want him to be able to be present to assist his wife during that period."

Where is Bob?

However, despite being granted a temporary reprieve from his prison sentence, Menendez was nowhere to be found on Monday during the morning's opening arguments or the afternoon's beginning of the presentation of evidence, according to the Post.

His attorney declined a request to explain his absence from the proceedings, but the outlet reported on speculation that he might be called later to testify by his wife's attorneys, which would justify his not being in the courtroom but wouldn't necessarily cover why he didn't at least escort her to and from the building.

Given that the judge specifically delayed the start of Menedez's sentence so that he could attend the trial in support of his wife, it will be interesting to see if he has anything to say about the noticeable absence.