have a mountain to climb
To have an extremely difficult, seemingly impossible task at hand. After losing Ohio to his opponent, the president now has a mountain to climb if he wants to hold on to his job. If I don't get some tangible results soon, I know I'll have a mountain to climb to get the board to continue to fund my research. I know I have a mountain to climb to clear my name, but I won't rest until I'm exonerated.
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