level best

My siblings all managed their level best to help but failed to see the daily load that crushed me.

“During the McCain campaign, I tried my dead-level best to make sure nobody knew anything,” he recounts.

He was humble and patient, an earnest man simply trying, by golly, to do his level best for others.

Nevertheless, President Bush, true to his campaign pledge, did his level best keep his foot on the pedal.

I'd have enjoyed punching his proud head, for all that; it was a dirty way to serve a man who had done his level best.

Their tongues and loud Rad ram's-horns do their level best to win it, Mum.

There's a breakdown gang doing its level best to get us clear.

But they were doing their level best to save the vessel: that was plain.

If you'll pay me ten dollars a week, Mr. Dart, I'll do my level best to earn it.