Celebrating a three-state sweep in the latest Democratic Party caucuses, Vermont Sen. Bernie Sanders said Sunday he believed campaign momentum had shifted in his favor and would position him to defeat Donald Trump.

Sanders beat Hillary Clinton by decisive margins in Hawaii, Alaska and Washington.

“Our calculations are that in fact we can win the pledged delegates,” Sanders said on NBC's  "Meet the Press" with Chuck Todd. “And at a time when we have the momentum, we have won five out of the six last contests in landslide fashion, in all of the national polling that I have seen, we are beating Donald Trump by much greater margins than is Secretary Clinton.”

Sen. Bernie Sanders put together a trifecta on Saturday -- lopsided wins in three caucuses that had his supporters cheering.

Unfortunately for Sanders' backers, however, the victories didn't do much to change the shape of a Democratic primary race in which Hillary Clinton remains the odds-on favorite.

How come? 

Federal prosecutors investigating the possible mishandling of classified materials on Hillary Clinton’s private email server have begun the process of setting up formal interviews with some of her longtime and closest aides, according to two people familiar with the probe, an indication that the inquiry is moving into its final phases.

Those interviews and the final review of the case, however, could still take many weeks, all but guaranteeing that the investigation will continue to dog Clinton’s presidential campaign through most, if not all, of the remaining presidential primaries.

No dates have been set for questioning the advisors, but a federal prosecutor in recent weeks has called their lawyers to alert them that he would soon be doing so, the sources said. Prosecutors also are expected to seek an interview with Clinton herself, though the timing remains unclear.

Ohio Gov. John Kasich, who has made a point of running a positive campaign as he seeks the Republican presidential nomination, waded into the personal back-and-forth between front-runner Donald Trump and Texas Sen. Ted Cruz that has taken shape in recent days. 

"Families have to be off-limits. I mean, you cannot get these attacks on families," Kasich said on NBC's "Meet the Press" on Sunday.

"And if this becomes the order of the day, what kind of people are we going to have in the future that are going to run for public office? There's got to be some rules ... some decency."