NEW HAVEN, Feb. 26--After playing Yale to a standoff in the first half, the Harvard basketball team abruptly crumbled and allowed the Elis to waltz to a 63-51 win here tonight.

Harvard, now with an Ivy record of four wins and eight losses, takes its tenuous hopes for a first division finish in the League to Providence tonight for a game with Brown.

Tied 32-32 at halftime tonight the Crimson took the lead at the start of the second half on Barry William's free throw, only to have Yale's Rick Johnson put the Bulldogs in front for the first time in the game with a jump shot from the foul line.

Then the heavens burst as Howard Dale of Yale hit another jump shot and teammate Bob Trupin added two more points on a breakaway. Scenting disaster. Harvard coach Floyd Wilson switched into zone defense, but the damage was done. Harvard never was close to the lead again.

The key to Yale's victory was the air-tight defensive job guard Herb Broadfoot applied to Harvard star Keith Sedlacek. Sedlacek, needing only 12 points to break the Harvard single season scoring record, got a total of just nine as Broadfoot crowded him incessantly, never allowing Sedlacek room enough for his accurate jump shots. Sedlacek was also hamstrung by three quick fouls picked up in the first five minutes of play.

Harvard had led from the start of the game, largely on the strength of voracious rebounding and accurate shooting by Williams and Merle McClung. Williams had eight rebounds at half time and eight points, while McClung had 11 points.

The Crimson's lead fluctuated all through the first half, growing at one time to seven points. But as time ran out the Bulldogs cut the margin to 32-30, and after Harvard tried unsuccessfully to hold the ball for one shot, Broadfoot hit a short jumper just before the buzzer to tie the score.

But after Yale exploded into the lead in the second half, the Elis' Don Taylor and Johnson ruled the boards and shut off any hopes Harvard might have had for a comeback.

McClung's shooting fell off as well; in one stretch he missed three moderately easy shots in a row and finished the game with only 15 points, tied with Dale for top scoring honors.