WASHINGTON, April 26 -- Democrat presidential contender Hillary Clinton was projected to win primaries in four out of five northeastern U.S. states on Tuesday, only losing Rhode Island to her rival Bernie Sanders, media outlets reported.

In Philadelphia, Clinton promised on Tuesday night to return for the party's national convention with the most votes and the most pledged delegates, according to an ABC news report.

All polls closed at 8 p.m. local time (0100 GMT, Wednesday). Clinton was projected winner in the Democrat primaries in Maryland, Connecticut, Delaware and delegate-rich Pennsylvania, which is the largest prize of Tuesday's contests.

The former secretary of state won the majority of the 189 pledged delegates awarded in Pennsylvania, enlarging her lead over Sanders and moving her toward the 2,383 delegates needed to clinch the nomination.

However, Sanders told ABC's "Good Morning America" on Tuesday that he is going to fight through California and "then we'll see what happens."

Clinton entered the day with 1,428 pledged delegates, compared with 1,153 for Sanders.

The next round of primaries in states, including Indiana, Oregon and West Virginia, are expected to offer Sanders better odds.

A poll from Harvard this week found Sanders has a high favorability rating among younger voters.