Senator Robert F. Kennedy is expected to win his second straight presidential primary victory in Nebraska today.

But two key questions remain to be answered by today's primary: the size of vice president Hubert H. Humphrey's vote and the magnitude of Kennedy's victory over Sen. Eugene J. McCarthy.

Nebraskans may indicate support for Humphrey either by writing in Humphrey's name--which is not on the ballot--or by voting for President Johnson--who is on the ballot. Humphrey entered the presidential race too late to have his name placed on the Nebraska ballot, and Johnson withdrew too late to have his removed.

McCarthy is expected to run well in Lancaster County (Lincoln), the home of the University of Nebraska, but is rumored to be in trouble in Omaha. Forty per cent of the Democratic vote is in Omaha.

Homogeneous

Nebraska is relatively homogeneous ethnically, except for a black ghetto in Omaha with 15,000 votes.

Both Kennedy and McCarthy have campaigned throughout the state during the past five weeks, though the New York Senator has spent much more time in Nebraska than McCarthy. Humphrey made one speech in Omaha during the primary campaign. Kennedy and McCarthy have both used large amounts of radio and television time in their campaigns.

Meanwhile, the Associated Press reported that a telephoned bomb threat rousted Kennedy staff members from their Omaha headquarters. Police searched the headquarters but found no bomb.